Fetal Growth Restriction

Complex MONDO:0005030 Pathograph 13 Show in embeddings browser Placental disease Pregnancy disorder Ischemic placental disease

Fetal growth restriction is the failure of a fetus to achieve its genetically determined growth potential, in the great majority of cases because the placenta cannot deliver enough oxygen and substrate to sustain it. The initiating lesion is the same one that underlies preeclampsia and placental abruption - deficient remodelling of the maternal uterine spiral arteries in early pregnancy - which is why the three are grouped as ischaemic placental disease. What distinguishes FGR is where the consequences land. In preeclampsia the stressed syncytiotrophoblast releases anti-angiogenic factors that produce a maternal endothelial syndrome; in FGR the damage is expressed almost entirely in the fetal compartment, as chronic hypoxaemia and nutrient deprivation. The intervening mechanism is a loss of exchange capacity rather than a single molecular lesion. Malperfusion imposes cell stress on the placenta that selectively suppresses protein synthesis and proliferation, shrinking villous volume and exchange surface area; imprinted and non-imprinted gene expression is extensively dysregulated, and placental system A amino acid transporter activity falls. The fetus responds with cardiovascular redistribution toward brain, heart and adrenals - "brain sparing" - which preserves the cerebral circulation at the cost of somatic growth and is therefore a sign of compensation, not of safety. Progressive placental deterioration is tracked by the umbilical artery Doppler waveform, whose absent or reversed end-diastolic flow correlates with dedifferentiation of the smooth muscle around the fetal stem villous arteries, and ends in metabolic acidosis and stillbirth. The entry's most consequential clinical fact is a negative one: there is no effective in-utero therapy. Every established intervention is surveillance plus timing of delivery, and the one mechanistically motivated attempt at treating the placenta directly - maternal sildenafil - failed in randomised trials. FGR is also distinct from "small for gestational age", which is a statistical statement about size rather than a statement about pathology: a constitutionally small fetus may be entirely healthy, and a normally-sized fetus may be growth restricted.

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2
Definitions
11
Pathophys.
3
Histopath.
11
Phenotypes
5
Gaps
13
Pathograph
2
Medical Actions
2
Subtypes
2
Differentials
📘

Definitions

2
Delphi consensus definition of early and late FGR
The internationally used case definition separates early FGR (< 32 weeks) from late FGR (>= 32 weeks) and, for each, distinguishes solitary parameters that are sufficient on their own from contributory parameters that require a second abnormality. Its structure is itself a mechanistic statement: absent end-diastolic flow in the umbilical artery is accepted as a solitary criterion for early FGR, meaning the placental-vascular lesion can establish the diagnosis without any size criterion being met.
DIAGNOSTIC_CRITERIA
Show evidence (2 references)
PMID:26909664 SUPPORT Human Clinical
"For early FGR (< 32 weeks), three solitary parameters (abdominal circumference (AC) < 3(rd) centile, estimated fetal weight (EFW) < 3(rd) centile and absent end-diastolic flow in the umbilical artery (UA)) and four contributory parameters (AC or EFW < 10(th) centile combined with a pulsatility..."
States the agreed solitary and contributory parameters for early FGR, including absent umbilical artery end-diastolic flow as a solitary criterion.
PMID:26909664 SUPPORT Human Clinical
"Consensus-based definitions for early and late FGR, as well as cut-off values for parameters involved, were agreed upon by a panel of experts."
Establishes that the early/late split and its cut-offs are expert-consensus derived.
Notes: Recorded as ESTABLISHED_CRITERIA rather than MECHANISTIC_HYPOTHESIS: this is a consensus case definition, not a case-finding query predicated on an unproven mechanism.
Fetal growth restriction versus small for gestational age
SGA is a statistical threshold on size relative to a reference population; FGR is a claim about failed growth potential from a pathological cause. The two sets overlap but neither contains the other, and conflating them is the single most common source of misclassification in the FGR literature - it dilutes cohorts with healthy small fetuses and misses growth-restricted fetuses of normal size.
DIAGNOSTIC_CRITERIA
Show evidence (3 references)
PMID:33972065 SUPPORT Human Clinical
"Fetuses can be constitutionally small or large and thus healthy, whereas fetuses with seemingly normal size can be growth restricted or overgrown."
States directly that size thresholds and growth pathology are non-equivalent in both directions.
PMID:33972065 SUPPORT Human Clinical
"However, both are statistical definitions of fetal size below or above a certain threshold related to a reference population, rather than referring to an abnormal condition."
Establishes that SGA/LGA are statistical rather than pathological categories.
PMID:32965939 SUPPORT Human Clinical
"FGR is generally defined as the failure of a fetus to achieve its full genetically determined growth potential due to pathologic etiologies, primarily placental dysfunction."
Gives the potential-based definition of FGR and names placental dysfunction as the dominant cause.
◆

Subtypes

2
Early-onset FGR (< 32 weeks)
FGR diagnosed before 32 weeks' gestational age. This is the more severe and the more overtly placental-vascular form: it is the one frequently accompanied by preeclampsia, and its consensus case definition accepts absent umbilical artery end-diastolic flow as a solitary criterion, so the placental-vascular lesion can establish the diagnosis with no size criterion met. The umbilical-artery arm of this entry's pathograph - stem villous arterial smooth muscle dedifferentiation through to absent or reversed end-diastolic flow - is therefore principally an early-FGR route.
Show evidence (2 references)
PMID:32965939 SUPPORT Human Clinical
"Early-onset FGR is usually more severe, often associated with preeclampsia, and easier to detect, whereas late-onset FGR is more common, subtle, and harder to diagnose."
States the severity, preeclampsia association and detectability that distinguish early-onset from late-onset FGR.
PMID:26909664 SUPPORT Human Clinical
"For early FGR (< 32 weeks), three solitary parameters (abdominal circumference (AC) < 3(rd) centile, estimated fetal weight (EFW) < 3(rd) centile and absent end-diastolic flow in the umbilical artery (UA)) and four contributory parameters (AC or EFW < 10(th) centile combined with a pulsatility..."
Fixes the < 32 week boundary for this subtype and records absent umbilical artery end-diastolic flow as a solitary diagnostic criterion for it.
Late-onset FGR (>= 32 weeks)
FGR diagnosed at or after 32 weeks' gestational age. It is the commoner but more subtle form, and is harder to detect. Its consensus definition drops absent end-diastolic flow as a solitary criterion and reaches instead for the cerebroplacental ratio or umbilical artery pulsatility index - a diagnostic shift that follows the mechanism, since the fetal cardiovascular-redistribution arm rather than frank umbilical-artery end-diastolic flow loss is what is measurable at this gestation.
Show evidence (2 references)
PMID:26909664 SUPPORT Human Clinical
"For late FGR (≥ 32 weeks), two solitary parameters (AC or EFW < 3(rd) centile) and four contributory parameters (EFW or AC < 10(th) centile, AC or EFW crossing centiles by > two quartiles on growth charts and cerebroplacental ratio < 5(th) centile or UA-PI > 95(th) centile) were defined."
Fixes the >= 32 week boundary for this subtype and shows that its contributory parameters use the cerebroplacental ratio and UA-PI rather than absent end-diastolic flow.
PMID:32965939 SUPPORT Human Clinical
"These parameters differed depending on whether FGR was early-onset FGR (<32 weeks gestational age) or late-onset FGR (≥32 weeks gestational age) based on gestational age at diagnosis"
Confirms that the diagnostic parameters themselves differ by the early/late gestational-age split.
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Discussions and Knowledge Gaps

5
Can placental function be improved in utero once deficient spiral artery remodeling is established, or is the therapeutic window closed by the end of the first trimester?
KNOWLEDGE GAP OPEN gap_fgr_no_in_utero_therapy
Attached to
pathophysiology#Deficient Uterine Spiral Artery Remodeling
This is the central unmet need of the entry and the reason its treatment section contains no disease-modifying therapy. The initiating lesion is laid down in early pregnancy, but FGR is not detected until the second or third trimester, so every candidate therapy is administered long after the remodeling failure is fixed. The STRIDER result is the strongest evidence available on this question: a drug with a coherent vasodilatory rationale, given to the right population, changed nothing - not pregnancy duration, not birthweight, not mortality. That null is consistent with the window having closed, but it does not distinguish this from the alternative explanation that sildenafil was simply the wrong agent.
Proposed experiments
First-trimester-initiated placental therapy in a high-risk cohort
exp_fgr_first_trimester_placental_therapy
Test a candidate placental therapy started in the first trimester in women selected by prior severe early-onset FGR or by first-trimester uterine artery Doppler, with placental histopathology and exchange-capacity imaging as intermediate endpoints rather than birthweight alone. This addresses the timing confound directly: a null result at that point would be evidence about the agent, whereas a null result in the third trimester is uninterpretable between agent and timing.
Show evidence (1 reference)
PMID:30169244 SUPPORT Human Clinical
"Sildenafil did not prolong pregnancy or improve pregnancy outcomes in severe early-onset fetal growth restriction and therefore it should not be prescribed for this indication outside of research studies with explicit participants' consent."
The negative randomised result that anchors the gap.
Does dedifferentiation of stem villous arterial smooth muscle cause the absent/reversed end-diastolic umbilical artery waveform, or are both downstream of a common placental vascular process?
KNOWLEDGE GAP OPEN gap_fgr_stem_villous_smc_causality
Attached to
pathophysiology#Stem Villous Arterial Smooth Muscle Dedifferentiation
The entry types this edge DIRECT because it is the best available mechanistic account of an otherwise unexplained imaging sign, but the source claims only a correlation, and the smooth muscle change is explicitly described as secondary. If the relationship is not causal, umbilical artery Doppler is a marker of placental disease severity rather than a readout of this specific lesion - which would not change how it is used clinically but would change what it licenses mechanistically. The same sentence is doing double duty in this entry: the word "Secondary" is also the only basis for the incoming INDIRECT_UNKNOWN_INTERMEDIATES edge from placental cell stress into this node, so if that ordering is wrong, both edges around this node are wrong together.
Show evidence (1 reference)
PMID:29422210 SUPPORT Human Clinical
"Secondary changes involving dedifferentiation of smooth muscle cells surrounding the fetal arteries within placental stem villi correlate with absent or reversed end-diastolic umbilical artery blood flow, and with a reduction in birthweight."
The source's own wording - "secondary changes" and "correlate with" - is what makes this a gap rather than an established mechanism.
Why is placental system A amino acid transport reduced in growth-restricted pregnancies without preeclampsia but not in growth-restricted pregnancies with preeclampsia, when both share the same spiral artery lesion?
KNOWLEDGE GAP OPEN gap_fgr_amino_acid_transport_not_universal
Attached to
pathophysiology#Impaired Placental Nutrient Transport
This is a genuine dissociation, not a null finding, and it constrains the model curated in this entry. If reduced amino acid transport were a simple downstream consequence of malperfusion, it should be present wherever malperfusion is - and it is most severe in FGR with preeclampsia, where the transport deficit is absent. The observation implies that the route from placental stress to fetal growth failure differs between the two presentations, which is why the entry does not treat FGR-with-preeclampsia as simply a more severe version of FGR alone.
Show evidence (1 reference)
PMID:18718657 SUPPORT Human Clinical
"We confirm the reduced uptake of amino acids in SGA pregnancies without preeclampsia but report that placental amino acid uptake of SGA infants with maternal preeclampsia is not reduced and is identical to uptake by normal and preeclamptic pregnancies with normal weight infants."
Reports the dissociation in full, including that the preeclamptic SGA placentas were indistinguishable from normal.
How much of the inconsistency in the FGR literature is attributable to cohorts assembled on size thresholds (SGA) rather than on growth pathology (FGR)?
KNOWLEDGE GAP OPEN gap_fgr_definition_heterogeneity
Attached to
pathophysiology#Failure to Achieve Genetically Determined Growth Potential
Any cohort defined by a size centile contains constitutionally small healthy fetuses and omits growth-restricted fetuses of normal size. Effect estimates from such cohorts are therefore biased toward the null by an unknown amount that varies with the threshold used and the reference population. The Delphi definition exists to fix this prospectively but cannot repair the retrospective literature, and the parallel problem in placental pathology is what the Amsterdam consensus addressed.
Show evidence (2 references)
PMID:33972065 SUPPORT Human Clinical
"Fetuses can be constitutionally small or large and thus healthy, whereas fetuses with seemingly normal size can be growth restricted or overgrown."
States the bidirectional misclassification that drives the gap.
PMID:27223167 SUPPORT Human Clinical
"The value of placental examination in investigations of adverse pregnancy outcomes may be compromised by sampling and definition differences between laboratories."
Documents the same definitional-heterogeneity problem on the placental pathology side.
Does the nanoplastic-to-placental-ferroptosis mechanism shown in gestationally exposed mice operate at the plastic burdens actually measured in human placentas, or only at experimental doses far above them?
HUMAN MODEL MISMATCH OPEN fgr_microplastic_dose_translation_mismatch
Attached to
pathophysiology#Placental Cell Stress Response environmental#Placental micro- and nanoplastic accumulation
The mechanism is not missing - it is worked out in unusual detail in rodents, down to a rescue arm. What is missing is the bridge to human exposure. Mice received 1-100 mg/kg/day of monodisperse 100 nm polystyrene by gavage for most of gestation; human placentas carry a mixed-polymer burden averaging roughly 127 micrograms per gram of tissue, acquired over years by ingestion and inhalation. The two differ in dose, in polymer identity, in particle size distribution, and in route. Until a human-relevant dose-response is established, a positive rodent result should not be read as evidence that environmental microplastic exposure causes FGR in people, and the negative case is equally open.
Proposed experiments
Placental burden versus oxidative and ferroptotic markers in human FGR
fgr_microplastic_burden_vs_ferroptosis_readouts
In prospectively collected placentas with recorded exposure history, pair quantitative polymer measurement (Py-GC-MS) with the ferroptosis and NAD-metabolism readouts the rodent work identifies, testing whether the proposed intermediates track burden within the human range rather than only above it.
Would support
pathophysiology#Placental Cell Stress Response
Supporting outcome
  • Placental NAD+ and nicotinamide fall, and lipid peroxidation markers rise, monotonically with measured polymer burden across the human range.
Refuting outcome
  • No relationship between polymer burden and the NAD/ferroptosis readouts across the human range, locating the rodent effect above environmental exposure.
Show evidence (2 references)
PMID:40796882 SUPPORT Model Organism
"pregnant mice were orally administered PS-NPs (approximately 100 nm in diameter) at different concentrations (1, 10, and 100 mg/kg/day) for 17.5 consecutive days"
States the administered dose, particle size and route that the human comparison has to be made against.
PMID:38366932 SUPPORT Human Clinical
"averaging 126.8 ± 147.5 µg/g (mean±SD). Polyethylene was the most prevalent polymer, accounting for 54% of total NMPs"
Gives the measured human placental burden and its dominant polymer, neither of which matches the rodent exposure.
⚙

Pathophysiology

11
Deficient Uterine Spiral Artery Remodeling
In normal pregnancy extravillous trophoblast invades the decidua and inner myometrium and converts the maternal spiral arteries into wide, flaccid, low-resistance conduits. When that conversion is deficient the arteries remain narrow and vasoreactive, and uteroplacental perfusion is fixed at an inadequate level from early pregnancy onward. This is the initiating lesion shared with preeclampsia and placental abruption.
extravillous trophoblast CL:0008036 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves extravillous trophoblast (CL:0008036). CL:0008036 is a cell type from the Cell Ontology.
maternal placenta development GO:0001893 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased maternal placenta development (GO:0001893). GO:0001893 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Uteroplacental Malperfusion Failure to convert the spiral arteries is what produces the malperfused intervillous space.
Show evidence (1 reference)
PMID:29422210 SUPPORT Human Clinical
"Placental-related fetal growth restriction arises primarily due to deficient remodeling of the uterine spiral arteries supplying the placenta during early pregnancy."
Establishes deficient spiral artery remodeling as the primary initiating lesion in placental FGR.
Uteroplacental Malperfusion
With the spiral arteries unconverted, perfusion of the intervillous space is inadequate from early pregnancy onward. This is a tissue-level perfusion failure of the uteroplacental unit - the haemodynamic state that the placental cells then have to respond to - and is the lesion that imaging of the intraplacental vasculature detects.
Downstream
Placental Cell Stress Response Malperfusion is what imposes cell stress on the placental tissues, and the stress response it induces is selective rather than indiscriminate.
Show evidence (1 reference)
PMID:33085318 SUPPORT Human Clinical
"The disorder generally involves inadequate placental perfusion, which leads to insufficient delivery of oxygen and nutrients to the fetus."
Names inadequate placental perfusion as the tissue-level perfusion failure at the centre of placental insufficiency.
Placental Cell Stress Response
The malperfused placenta experiences oxidative and endoplasmic reticulum stress. The cellular response is not indiscriminate injury but a selective shutdown - protein synthesis is suppressed and proliferation falls - which is why the placenta becomes small and hypoplastic rather than simply necrotic. In more severe cases infarction and fibrin deposition are superimposed.
syncytiotrophoblast CL:0000525 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves syncytiotrophoblast, annotated with syncytiotrophoblast cell (CL:0000525). CL:0000525 is a cell type from the Cell Ontology.
response to hypoxia GO:0001666 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased response to hypoxia (GO:0001666). GO:0001666 is a biological process from the Gene Ontology. ↑ INCREASED cytoplasmic translation GO:0002181 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased cytoplasmic translation (GO:0002181). GO:0002181 is a biological process from the Gene Ontology. ↓ DECREASED cell population proliferation GO:0008283 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased cell population proliferation (GO:0008283). GO:0008283 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Reduced Villous Volume and Exchange Surface Area Suppressed protein synthesis and proliferation, compounded by infarction and fibrin deposition, reduce the villous tissue available for exchange.
Impaired Placental Nutrient Transport Placental stress drives extensive dysregulation of imprinted and non-imprinted gene expression, which alters transport function specifically - a change in transporter capacity that is separate from the loss of surface area.
Stem Villous Arterial Smooth Muscle Dedifferentiation The source calls the stem villous arterial change "secondary", placing it downstream of the placental disease process rather than alongside it, but does not name what it is secondary to or by what route. The edge is drawn so the fetal-side arm is not left hanging as an independent initiating lesion, and typed INDIRECT_UNKNOWN_INTERMEDIATES because the intervening steps are genuinely unstated.
Show evidence (1 reference)
PMID:29422210 SUPPORT Human Clinical
"These effects are compounded in more severe cases by increased infarction and fibrin deposition."
Records the superimposed infarction and fibrin deposition seen in severe disease.
Reduced Villous Volume and Exchange Surface Area
The structural endpoint of placental stress is a smaller placenta with less villous tissue and less surface area across which maternal-fetal exchange can occur. This is the anatomical substrate of placental insufficiency, and is what the histopathological pattern of distal villous hypoplasia describes.
placenta blood vessel development GO:0060674 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased placenta blood vessel development (GO:0060674). GO:0060674 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Chronic Fetal Hypoxemia and Nutrient Deprivation Reduced exchange capacity is what limits delivery of oxygen and substrate to the fetus.
Show evidence (1 reference)
PMID:29422210 SUPPORT Human Clinical
"Consequently, there is a reduction in villous volume and surface area for maternal-fetal exchange."
Directly states the reduction in villous volume and exchange surface area.
Impaired Placental Nutrient Transport
Independently of how much surface area remains, the transporters themselves carry less. System A amino acid transporter activity is reduced in placentas from growth-restricted pregnancies, and the affected infants have lower circulating amino acid concentrations. The imprinted Igf2-H19 locus is a principal regulator of this supply-demand matching, which is why imprinted gene dysregulation translates into a nutrient-transfer deficit.
amino acid transmembrane transport GO:0003333 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased amino acid transmembrane transport (GO:0003333). GO:0003333 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Chronic Fetal Hypoxemia and Nutrient Deprivation Reduced placental amino acid transport lowers the substrate actually reaching the fetal circulation.
Show evidence (2 references)
PMID:18718657 SUPPORT Human Clinical
"We confirm the reduced uptake of amino acids in SGA pregnancies without preeclampsia but report that placental amino acid uptake of SGA infants with maternal preeclampsia is not reduced"
Confirms reduced system A uptake in SGA without preeclampsia, and is curated deliberately with its negative half intact - the transport deficit was NOT found when the same growth restriction occurred alongside preeclampsia, so reduced amino acid transport cannot be assumed to be a universal feature of every growth-restricted placenta.
PMID:16612114 SUPPORT Model Organism
"They affect the growth, morphology and nutrient transfer capacity of the placenta and, thereby, control the nutrient supply for fetal growth."
Places imprinted genes upstream of placental nutrient transfer capacity. Tagged MODEL_ORGANISM because the mechanistic dissection cited is the murine Igf2P0 and Igf2-null comparison.
Chronic Fetal Hypoxemia and Nutrient Deprivation
The fetal-compartment consequence of placental insufficiency: a sustained, progressive shortfall of oxygen and substrate. It is chronic rather than acute, which is what allows the adaptive responses below to develop and what distinguishes the FGR trajectory from an acute event such as abruption.
response to hypoxia GO:0001666 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased response to hypoxia (GO:0001666). GO:0001666 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
Fetal Cardiovascular Redistribution (Brain Sparing) Hypoxaemia is the direct trigger for redistribution of fetal cardiac output toward the brain and other vital organs.
Failure to Achieve Genetically Determined Growth Potential Substrate shortfall directly limits somatic growth, which is the defining manifestation of the disease.
Show evidence (1 reference)
PMID:33085318 SUPPORT Human Clinical
"Current understanding characterizes the condition as a progressive decline in placental function that culminates in chronic fetal hypoxemia, metabolic acidosis, and FGR."
States the progressive placental decline culminating in chronic fetal hypoxemia.
Fetal Cardiovascular Redistribution (Brain Sparing)
The hypoxaemic fetus preferentially perfuses brain, myocardium and adrenals at the expense of the splanchnic bed, kidneys, skeleton and muscle. The clinical corollary matters: brain sparing is measured as a fall in the cerebroplacental ratio and is the reason growth restriction is often asymmetric, with abdominal circumference falling away before head circumference. It is a marker of successful compensation, not of a fetus that is safe.
Downstream
Failure to Achieve Genetically Determined Growth Potential Diverting cardiac output away from the splanchnic and musculoskeletal beds is part of why somatic growth stops, and why the restriction is typically asymmetric.
Show evidence (1 reference)
PMID:33085318 SUPPORT Human Clinical
"Physiologically, hypoxemia triggers adaptive fetal responses, including redistribution of blood flow toward vital organs (brain sparing), diminished fetal movement, and reduced somatic growth."
Directly describes brain sparing as redistribution of blood flow toward vital organs.
Stem Villous Arterial Smooth Muscle Dedifferentiation
A change on the fetal side of the placenta, distinct from the maternal spiral artery lesion that started the disease. Smooth muscle cells surrounding the fetal arteries within the placental stem villi dedifferentiate, and this correlates with the umbilical artery Doppler abnormality used clinically to grade severity. Curating it as its own node is what makes absent/reversed end-diastolic flow a mechanistic readout of placental vascular pathology rather than an unexplained imaging sign.
placental stem villous arterial smooth muscle cell CL:0009093 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves placental stem villous arterial smooth muscle cell, annotated with smooth muscle cell of placenta (CL:0009093). CL:0009093 is a cell type from the Cell Ontology.
Downstream
Absent or Reversed Umbilical Artery End-Diastolic Flow Dedifferentiation of the smooth muscle around the fetal stem villous arteries is the correlate of the abnormal umbilical artery waveform. Note the source claims correlation, not demonstrated causation - see the linked knowledge gap.
Show evidence (1 reference)
PMID:29422210 SUPPORT Human Clinical
"Secondary changes involving dedifferentiation of smooth muscle cells surrounding the fetal arteries within placental stem villi correlate with absent or reversed end-diastolic umbilical artery blood flow, and with a reduction in birthweight."
Establishes the fetal stem villous arterial change and its correlation with birthweight reduction.
Absent or Reversed Umbilical Artery End-Diastolic Flow
Rising placental vascular resistance first blunts, then abolishes, and finally reverses diastolic flow in the umbilical artery. This is the principal surveillance axis in early FGR and, in the consensus case definition, absent end-diastolic flow is on its own sufficient to diagnose early FGR without any size criterion.
Downstream
Fetal Metabolic Acidosis and Decompensation Deterioration of the umbilical artery waveform marks progression toward metabolic acidosis, but the ordering and the intervening steps between Doppler deterioration and acidaemia are inferred from surveillance sequences rather than from a demonstrated mechanism.
Show evidence (1 reference)
PMID:26909664 SUPPORT Human Clinical
"For early FGR (< 32 weeks), three solitary parameters (abdominal circumference (AC) < 3(rd) centile, estimated fetal weight (EFW) < 3(rd) centile and absent end-diastolic flow in the umbilical artery (UA)) and four contributory parameters (AC or EFW < 10(th) centile combined with a pulsatility..."
Records absent umbilical artery end-diastolic flow as a solitary diagnostic criterion for early FGR.
Failure to Achieve Genetically Determined Growth Potential
The defining manifestation. Framed as failure against the fetus's own potential rather than against a population centile, which is what separates FGR from constitutional smallness.
Downstream
Fetal Metabolic Acidosis and Decompensation Continuing placental decline in an already growth-restricted fetus progresses to acidaemia; the growth deficit itself is a marker of the severity of the supply failure rather than a cause of the acidosis.
Show evidence (1 reference)
PMID:32965939 SUPPORT Human Clinical
"FGR is generally defined as the failure of a fetus to achieve its full genetically determined growth potential due to pathologic etiologies, primarily placental dysfunction."
Defines the node in the terms used by the field.
Fetal Metabolic Acidosis and Decompensation
The terminal step, in which compensation fails: oxygen delivery falls below what anaerobic metabolism can offset, lactate accumulates and the fetus becomes acidaemic. It is the event that the entire surveillance apparatus exists to anticipate, because its endpoint is stillbirth and the only available intervention - delivery - must be taken before it occurs.
Show evidence (2 references)
PMID:33085318 SUPPORT Human Clinical
"Current understanding characterizes the condition as a progressive decline in placental function that culminates in chronic fetal hypoxemia, metabolic acidosis, and FGR."
Names metabolic acidosis as the culmination of progressive placental decline.
PMID:32965939 SUPPORT Human Clinical
"Fetal growth restriction (FGR) is a common pregnancy complication worldwide, leading to stillbirth and neonatal mortality and morbidity."
Records stillbirth and neonatal death as the outcomes of the decompensated state.
✶

Histopathology

3
Maternal Vascular Malperfusion
The consensus placental-pathology diagnosis corresponding to the maternal spiral artery lesion. The Amsterdam Placental Workshop Group statement is what standardised this terminology; before it, laboratories used incompatible definitions, which is a large part of why the older clinicopathological literature on FGR is hard to compare.
Show evidence (2 references)
PMID:27223167 SUPPORT Human Clinical
"The terminology and microscopic descriptions for maternal vascular malperfusion, fetal vascular malperfusion, delayed villous maturation, patterns of ascending intrauterine infection, and villitis of unknown etiology were agreed upon."
Establishes maternal vascular malperfusion as a consensus-defined placental lesion category.
PMID:27223167 SUPPORT Human Clinical
"The value of placental examination in investigations of adverse pregnancy outcomes may be compromised by sampling and definition differences between laboratories."
Records why the standardisation was needed, and hence the comparability caveat on older literature.
Distal Villous Hypoplasia and Increased Syncytial Knots
The microscopic correlate of reduced villous volume and exchange surface area - sparse, thin distal villi with increased syncytial knotting, accompanied by infarction and fibrin deposition.
Show evidence (2 references)
PMID:33085318 SUPPORT Human Clinical
"Histopathologic patterns commonly linked to placental insufficiency include distal villous hypoplasia, increased syncytial knots, maternal vascular malperfusion, placental infarctions, and fibrin deposition."
Enumerates the histopathological pattern associated with placental insufficiency.
PMID:29422210 SUPPORT Human Clinical
"These effects are compounded in more severe cases by increased infarction and fibrin deposition."
Confirms infarction and fibrin deposition as severity-associated findings.
Placental Lesions in FGR with Preeclampsia
Growth restriction accompanied by preeclampsia shows more severe placental damage than growth restriction alone. This is a useful piece of evidence for the two-outcome model: the same initiating lesion, at a higher level of placental stress, additionally produces the maternal syndrome.
Show evidence (2 references)
PMID:29422210 SUPPORT Human Clinical
"The changes are more severe in cases of growth restriction associated with preeclampsia compared to those with growth restriction alone, consistent with the greater degree of maternal vasculopathy reported in the former and more extensive macroscopic placental damage including infarcts,..."
Directly contrasts placental lesion severity between FGR with and without preeclampsia.
PMID:29422210 SUPPORT Human Clinical
"The higher level of stress may activate proinflammatory and apoptotic pathways within the syncytiotrophoblast, releasing factors that cause the maternal endothelial cell activation that distinguishes between the 2 conditions."
Gives the proposed mechanism by which the shared lesion diverges into FGR alone versus FGR with preeclampsia. Marked PARTIAL to match the source's own hedge - "may activate" - which is why this is curated as histopathological interpretation rather than as an asserted causal edge.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Fetal Growth Restriction Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

11
Blood 1
Polycythemia HP:0001901 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Polycythemia (HP:0001901). HP:0001901 is a phenotype from the Human Phenotype Ontology.
No evidence item attached, for the same reason as the hypoglycaemia phenotype above.
Metabolism 1
Neonatal Hypoglycemia HP:0001943 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Neonatal hypoglycemia, annotated with Hypoglycemia (HP:0001943), qualified as temporality transient. HP:0001943 is a phenotype from the Human Phenotype Ontology.
Temporal: TRANSIENT
No evidence item is attached. This is standard neonatal teaching, but none of the references cached for this entry states it in a form that can be quoted as an exact snippet, and fabricating one would violate the evidence SOP. Recorded per the SOP's option of keeping the description without an evidence block.
Nervous System 1
Adverse Neurodevelopmental Outcome Global developmental delay HP:0001263 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:25747582 SUPPORT Human Clinical
"The primary outcome was survival without cerebral palsy or neurosensory impairment, or a Bayley III developmental score of less than 85, at 2 years of age."
Defines the composite neurodevelopmental outcome used as the trial primary endpoint in severe FGR.
PMID:30169244 SUPPORT Human Clinical
"Severe early-onset fetal growth restriction can lead to a range of adverse outcomes including fetal or neonatal death, neurodisability, and lifelong risks to the health of the affected child."
States neurodisability and lifelong health risk among the outcomes of severe early-onset FGR.
Prenatal and Birth 6
Absent End-Diastolic Umbilical Artery Flow HP:0034224 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Absent end-diastolic umbilical artery flow (HP:0034224). HP:0034224 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:26909664 SUPPORT Human Clinical
"For early FGR (< 32 weeks), three solitary parameters (abdominal circumference (AC) < 3(rd) centile, estimated fetal weight (EFW) < 3(rd) centile and absent end-diastolic flow in the umbilical artery (UA)) and four contributory parameters (AC or EFW < 10(th) centile combined with a pulsatility..."
Lists absent umbilical artery end-diastolic flow as a solitary criterion.
Abnormal Umbilical Artery Doppler Waveform Abnormal umbilical artery doppler waveform during pregnancy HP:0025715 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Elevated umbilical artery pulsatility index, annotated with Abnormal umbilical artery doppler waveform during pregnancy (HP:0025715). HP:0025715 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25747582 SUPPORT Human Clinical
"high umbilical artery Doppler pulsatility index"
Uses raised umbilical artery pulsatility index as a trial entry criterion defining very preterm FGR.
Decreased Fetal Movement HP:0001558 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Decreased fetal movement (HP:0001558). HP:0001558 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33085318 SUPPORT Human Clinical
"Physiologically, hypoxemia triggers adaptive fetal responses, including redistribution of blood flow toward vital organs (brain sparing), diminished fetal movement, and reduced somatic growth."
Lists diminished fetal movement among the adaptive responses to hypoxemia.
Oligohydramnios HP:0001562 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Oligohydramnios (HP:0001562). HP:0001562 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33085318 SUPPORT Human Clinical
"Placental insufficiency, also known as uteroplacental insufficiency, contributes to a broad spectrum of obstetric complications, including preeclampsia, fetal growth restriction (FGR), oligohydramnios, and stillbirth."
Lists oligohydramnios among the complications of placental insufficiency.
Fetal Distress HP:0025116 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Fetal distress (HP:0025116). HP:0025116 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25747582 SUPPORT Human Clinical
"We aimed to assess whether changes in the fetal ductus venosus Doppler waveform (DV) could be used as indications for delivery instead of cardiotocography short-term variation (STV)."
Establishes reduced cardiotocograph short-term variation as the comparator indication for delivery, i.e. the standard marker of fetal compromise.
Preterm Birth Premature birth HP:0001622 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Premature birth (HP:0001622). HP:0001622 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25747582 SUPPORT Human Clinical
"The median gestational age at delivery was 30"
Quantifies gestational age at delivery in a severe early-onset FGR trial cohort. The quote is truncated before the decimal separator because the source renders it with a middle dot.
Growth 1
Failure of Fetal Growth Intrauterine growth retardation HP:0001511 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Fetal growth restriction, annotated with Intrauterine growth retardation (HP:0001511), qualified as course progressive. HP:0001511 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:32965939 SUPPORT Human Clinical
"FGR is generally defined as the failure of a fetus to achieve its full genetically determined growth potential due to pathologic etiologies, primarily placental dysfunction."
The defining phenotype of the entry.
Other 1
Stillbirth
Deliberately left without a phenotype_term. The correct HPO term, HP:0003826 Stillbirth, sits under Clinical modifier / Clinical course (HP:0031797) rather than under Phenotypic abnormality (HP:0000118), and the PhenotypeTerm dynamic enum is rooted at HP:0000118, so the term cannot be bound here without failing validation. Verified with `runoak -i sqlite:obo:hp ancestors -p i,p HP:0003826`. Binding a different, wrong term or dropping the phenotype would both be worse than leaving it unbound with this note. This is the fourth dismech entry to hit the same structural gap - see issue #7837 gap 3, plus Familial_Hyperaldosteronism_Type_I (HP:0100602), Intrahepatic_Cholestasis_of_Pregnancy and Hemolytic_Disease_of_the_Fetus_and_Newborn (both stillbirth).
Show evidence (1 reference)
PMID:32965939 SUPPORT Human Clinical
"Fetal growth restriction (FGR) is a common pregnancy complication worldwide, leading to stillbirth and neonatal mortality and morbidity."
States stillbirth as a leading outcome of FGR.
💊

Medical Actions

2
Doppler and Cardiotocograph Surveillance with Timed Delivery
Action: Therapeutic ProcedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Therapeutic Procedure (NCIT:C49236). NCIT:C49236 is a clinical intervention from the NCI Thesaurus. NCIT:C49236
Platform: Other
The definitive management of FGR is not treatment of the fetus or placenta but surveillance and a decision about when to deliver, balancing the risk of continued intrauterine deterioration against the risk of prematurity. The TRUFFLE trial tested which surveillance signal should trigger delivery in very preterm FGR and found that using late ductus venosus changes was associated with better 2-year neurodevelopmental outcomes among survivors, though with a non-significant increase in mortality - a trade-off that the entry records rather than resolves.
Mechanism Target:
INHIBITS Fetal Metabolic Acidosis and Decompensation — Delivery removes the fetus from the failing placental supply before acidosis and death occur. It does not act on any upstream node - it truncates the trajectory, which is why the effect is recorded against the terminal node rather than against the placental lesion.
Show evidence (1 reference)
PMID:25747582 SUPPORT Human Clinical
"No consensus exists for the best way to monitor and when to trigger delivery in mothers of babies with fetal growth restriction."
Frames timing of delivery as the intervention lever, and records that the optimal trigger was unsettled.
Show evidence (2 references)
PMID:25747582 SUPPORT Human Clinical
"late changes in the DV waveform might produce an improvement in developmental outcomes at 2 years of age."
Reports the trial's interpretation. Marked PARTIAL, matching the authors' own hedging: the primary endpoint difference was non-significant, and the favourable survivor outcome came with a non-significant increase in mortality.
PMID:25747582 SUPPORT Human Clinical
"Although the difference in the proportion of infants surviving without neuroimpairment was non-significant at the primary endpoint"
Records the non-significant primary endpoint explicitly, so the entry does not overstate the trial result.
Maternal Sildenafil
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: sildenafil CHEBI:9139 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses sildenafil (CHEBI:9139). CHEBI:9139 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
A mechanistically motivated attempt to treat the placental lesion itself: phosphodiesterase-5 inhibition potentiates nitric oxide and was expected to vasodilate the uterine vessels and improve fetal growth. It did not work. The STRIDER trial found no effect on any outcome, and the drug should not be used for this indication. It is curated here because a well-reasoned negative is a real constraint on the mechanism - it is evidence that late pharmacological vasodilatation cannot reverse an established early-pregnancy remodelling failure.
Show evidence (3 references)
PMID:30169244 SUPPORT Human Clinical
"Sildenafil, a phosphodiesterase type 5 inhibitor, potentiates the actions of nitric oxide, which leads to vasodilatation of the uterine vessels and might improve fetal growth in utero."
States the mechanistic rationale that motivated the trial.
PMID:30169244 REFUTE Human Clinical
"Sildenafil did not prolong pregnancy or improve pregnancy outcomes in severe early-onset fetal growth restriction and therefore it should not be prescribed for this indication outside of research studies with explicit participants' consent."
Refutes benefit and issues an explicit recommendation against use for this indication.
PMID:30169244 REFUTE Human Clinical
"and birthweight (-14 g,-100 to 126; p=0"
Gives the null birthweight effect estimate. The quote is truncated before the p-value's decimal separator because the source renders it with a middle dot.
🌍

Environmental Factors

1
Placental micro- and nanoplastic accumulation
exposure to microplastic particle ECTO:7000061 Environmental Conditions, Treatments and Exposures Ontology (ECTO) Relation: this environmental factor is this exposure This environmental factor is exposure to microplastic particle (ECTO:7000061). ECTO:7000061 is an exposure from the Environmental Conditions, Treatments and Exposures Ontology.
Micro- and nanoplastic particles reach the maternal-fetal interface, and with sensitive analytical methods they are recovered from essentially every human placenta examined. That the exposure occurs is settled; that it restricts fetal growth is not. The human evidence is a small case-control series in which placentas were sampled at delivery, so it cannot separate an effect of the particles from preferential accumulation in an already-failing, malperfused placenta - and the authors themselves report a non-monotonic dose-response. The mechanistic case comes from rodent gestational-exposure experiments at doses well above documented human tissue burdens. This entry is curated as a plausible but unproven exposure, and the causal edges below are graded to that standard rather than to the strength of the detection studies.
Show evidence (2 references)
PMID:38366932 SUPPORT Human Clinical
"microplastics were present in all participants' placentae, with concentrations ranging widely from 6.5 to 685 µg NMPs per gram of placental tissue"
Quantifies the plastic burden of human placental tissue and shows it is universal in the sampled cohort, which is the premise for treating placental microplastics as an exposure at this interface at all.
PMID:33395930 SUPPORT Human Clinical
"12 microplastic fragments (ranging from 5 to 10 μm in size), with spheric or irregular shape were found in 4 placentas (5 in the fetal side, 4 in the maternal side and 3 in the chorioamniotic membranes)"
The first demonstration that particles cross to the fetal side and the chorioamniotic membranes, not only the maternal surface, establishing that the fetal compartment is reached.
Mechanism Target:
PREDISPOSES Failure to Achieve Genetically Determined Growth Potential — Placental microplastic count correlates inversely with birth weight and other neonatal anthropometry among growth-restricted pregnancies. The edge is drawn to the growth-failure node rather than to a placental mechanism because no intermediate step was measured. Direction of causation is unresolved: placentas were collected at delivery, particles were near or below the detection limit in almost all normal pregnancies, and a small dysfunctional placenta may concentrate or retain particles differently from a healthy one. Treat this as a signal worth testing prospectively, not as an established cause of FGR.
Show evidence (2 references)
PMID:36113646 SUPPORT Human Clinical
"MPs were found in all (13 out of 13) intrauterine growth restriction (IUGR) pregnancies and their average abundance ranged from 2 to 38 particles per placenta, but were less than limit of detection (LOD) in normal pregnancies except three out of 30 subjects"
Reports the case-control contrast the edge rests on. PARTIAL because it is cross-sectional with 13 IUGR placentas and establishes co-occurrence rather than a direction of effect.
PMID:36113646 SUPPORT Human Clinical
"Inverse associations between MPs exposure and birth outcomes were observed in terms of birth weight (r = - 0.82, p < 0.001), length (r = - 0.56, p < 0.001), head circumference (r = - 0.50, p = 0.001), and 1-min Apgar score (r = - 0.75, p < 0.001) among those with IUGR"
Quantifies the dose-response with the growth outcome this node names. PARTIAL for the same reason, and because the same paper reports the relationship is non-monotonic.
TRIGGERS Placental Cell Stress Response — In gestationally exposed mice, polystyrene nanoplastics deplete placental nicotinamide and NAD+, which lowers ATP production and drives oxidative stress and ferroptosis - the same oxidative and energetic failure this node describes, but reached without malperfusion upstream. Rescue by nicotinamide supplementation and reproduction of the placental injury by faecal transfer from exposed dams make the chain interventional rather than merely correlative. It remains a rodent result at doses above measured human placental burdens; see the human-model mismatch discussion.
Show evidence (2 references)
PMID:40796882 SUPPORT Model Organism
"PS-NPs exposure observably reduced the levels of nicotinamide (NAM) and nicotinamide adenine dinucleotide (NAD+) in the placenta, resulting in decreased ATP production, increased oxidative stress and ferroptosis"
Names the intermediates - NAM/NAD+ depletion, ATP loss, oxidative stress - that make this an indirect edge with known steps into the placental stress node.
PMID:40796882 SUPPORT Model Organism
"Treatment with NAM effectively mitigated disruptions in placental metabolism and reversed the adverse pregnancy outcomes caused by PS-NPs"
A rescue experiment: restoring the depleted intermediate reverses the outcome, which is what distinguishes this from an observed association.
🔬

Diagnosis

2
Ultrasound Biometry with Doppler Velocimetry
Diagnosis rests on serial ultrasound estimation of fetal weight and abdominal circumference against gestational-age references, combined with umbilical, uterine and middle cerebral artery Doppler. The Doppler component is not merely confirmatory - it carries diagnostic weight of its own in the consensus definition, and it is the axis on which severity and timing decisions are made.
Show evidence (1 reference)
PMID:26909664 SUPPORT Human Clinical
"two solitary parameters (AC or EFW < 3(rd) centile) and four contributory parameters (EFW or AC < 10(th) centile, AC or EFW crossing centiles by > two quartiles on growth charts and cerebroplacental ratio < 5(th) centile or UA-PI > 95(th) centile) were defined."
Sets out the biometric and Doppler parameters for diagnosing late FGR, including centile crossing and cerebroplacental ratio.
Absence of a Pathognomonic Marker
There is no single test that establishes placental insufficiency. Diagnosis is a composite judgement from biometry, Doppler and growth trajectory, and the lack of a definitive marker is itself a documented obstacle to uniform diagnosis and to comparability between studies.
Show evidence (2 references)
PMID:33085318 SUPPORT Human Clinical
"Recent evidence underscores the lack of a pathognomonic clinical or histologic marker, creating challenges in achieving uniform diagnosis and study of placental insufficiency."
States the absence of a pathognomonic marker and its consequences for diagnosis and research.
PMID:33085318 SUPPORT Human Clinical
"Despite extensive research, no universally accepted definition has been established."
Records that even the definition of the underlying placental insufficiency remains unsettled.
⚖️

Clinical Burden

High
FGR is among the largest contributors to stillbirth and to neonatal death and morbidity worldwide, and the affected child carries elevated risk well beyond the neonatal period. Its burden is amplified by the absence of any in-utero treatment: the only lever available is deciding when to deliver a fetus that is deteriorating in utero but immature outside it.
Show evidence (2 references)
PMID:32965939 SUPPORT Human Clinical
"Fetal growth restriction (FGR) is a common pregnancy complication worldwide, leading to stillbirth and neonatal mortality and morbidity."
States the global frequency and the principal adverse outcomes.
PMID:33085318 SUPPORT Human Clinical
"This condition accounts for a substantial proportion of global perinatal morbidity and mortality."
Attributes a substantial share of global perinatal morbidity and mortality to the underlying placental insufficiency.
🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Fetal Growth Restriction:

Constitutionally Small for Gestational Age
Overlapping Features A healthy fetus that is small because its growth potential is small. This is the single most important differential, because it is the majority of fetuses below the 10th centile and because treating it as FGR leads to iatrogenic preterm delivery. Normal Doppler indices and growth that tracks along its own centile rather than crossing centiles are what distinguish it.
Distinguishing Features
  • Normal umbilical and uterine artery Doppler indices
  • Normal amniotic fluid volume
  • Growth velocity maintained along a consistent centile rather than crossing centiles
  • No maternal vascular disease
Show evidence (2 references)
PMID:33972065 SUPPORT Human Clinical
"Fetuses can be constitutionally small or large and thus healthy, whereas fetuses with seemingly normal size can be growth restricted or overgrown."
States that constitutional smallness and growth restriction are distinct.
PMID:26909664 SUPPORT Human Clinical
"two solitary parameters (AC or EFW < 3(rd) centile) and four contributory parameters (EFW or AC < 10(th) centile, AC or EFW crossing centiles by > two quartiles on growth charts and cerebroplacental ratio < 5(th) centile or UA-PI > 95(th) centile) were defined."
The contributory-parameter structure is precisely the discriminator: being under the 10th centile is not sufficient without centile crossing or a Doppler abnormality.
Preeclampsia MONDO:0005081
Overlapping Features Shares the initiating spiral artery lesion with FGR and frequently coexists with it, but is defined by the maternal syndrome of hypertension and end-organ involvement. It is a differential in the sense that growth restriction should prompt evaluation for preeclampsia, not that the two are mutually exclusive.
Distinguishing Features
  • Maternal hypertension with proteinuria or other end-organ dysfunction
  • More severe placental lesions when growth restriction and preeclampsia coexist
  • Placental system A amino acid transport unexpectedly preserved in the combination
Show evidence (1 reference)
PMID:29422210 SUPPORT Human Clinical
"The changes are more severe in cases of growth restriction associated with preeclampsia compared to those with growth restriction alone, consistent with the greater degree of maternal vasculopathy reported in the former and more extensive macroscopic placental damage including infarcts,..."
Contrasts the two presentations on placental lesion severity.
{ }

Source YAML

click to show 
name: Fetal Growth Restriction
creation_date: "2026-08-15T06:00:00Z"
category: Complex
synonyms:
- FGR
- Intrauterine growth restriction
- IUGR
- Intrauterine growth retardation
- Fetal growth retardation
description: >
  Fetal growth restriction is the failure of a fetus to achieve its genetically
  determined growth potential, in the great majority of cases because the
  placenta cannot deliver enough oxygen and substrate to sustain it. The
  initiating lesion is the same one that underlies preeclampsia and placental
  abruption - deficient remodelling of the maternal uterine spiral arteries in
  early pregnancy - which is why the three are grouped as ischaemic placental
  disease. What distinguishes FGR is where the consequences land. In
  preeclampsia the stressed syncytiotrophoblast releases anti-angiogenic factors
  that produce a maternal endothelial syndrome; in FGR the damage is expressed
  almost entirely in the fetal compartment, as chronic hypoxaemia and nutrient
  deprivation.

  The intervening mechanism is a loss of exchange capacity rather than a single
  molecular lesion. Malperfusion imposes cell stress on the placenta that
  selectively suppresses protein synthesis and proliferation, shrinking villous
  volume and exchange surface area; imprinted and non-imprinted gene expression
  is extensively dysregulated, and placental system A amino acid transporter
  activity falls. The fetus responds with cardiovascular redistribution toward
  brain, heart and adrenals - "brain sparing" - which preserves the cerebral
  circulation at the cost of somatic growth and is therefore a sign of
  compensation, not of safety. Progressive placental deterioration is tracked by
  the umbilical artery Doppler waveform, whose absent or reversed end-diastolic
  flow correlates with dedifferentiation of the smooth muscle around the fetal
  stem villous arteries, and ends in metabolic acidosis and stillbirth.

  The entry's most consequential clinical fact is a negative one: there is no
  effective in-utero therapy. Every established intervention is surveillance
  plus timing of delivery, and the one mechanistically motivated attempt at
  treating the placenta directly - maternal sildenafil - failed in randomised
  trials. FGR is also distinct from "small for gestational age", which is a
  statistical statement about size rather than a statement about pathology: a
  constitutionally small fetus may be entirely healthy, and a normally-sized
  fetus may be growth restricted.
disease_term:
  preferred_term: fetal growth restriction
  term:
    id: MONDO:0005030
    label: fetal growth restriction
parents:
- Placental disease
- Pregnancy disorder
- Ischemic placental disease

has_subtypes:
- name: Early FGR
  display_name: Early-onset FGR (< 32 weeks)
  description: >
    FGR diagnosed before 32 weeks' gestational age. This is the more severe and
    the more overtly placental-vascular form: it is the one frequently
    accompanied by preeclampsia, and its consensus case definition accepts
    absent umbilical artery end-diastolic flow as a solitary criterion, so the
    placental-vascular lesion can establish the diagnosis with no size criterion
    met. The umbilical-artery arm of this entry's pathograph - stem villous
    arterial smooth muscle dedifferentiation through to absent or reversed
    end-diastolic flow - is therefore principally an early-FGR route.
  evidence:
  - reference: PMID:32965939
    reference_title: Fetal Growth Restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Early-onset FGR is usually more severe, often associated with preeclampsia, and easier to detect, whereas late-onset FGR is more common, subtle, and harder to diagnose."
    explanation: States the severity, preeclampsia association and detectability that distinguish early-onset from late-onset FGR.
  - reference: PMID:26909664
    reference_title: "Consensus definition of fetal growth restriction: a Delphi procedure."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For early FGR (< 32 weeks), three solitary parameters (abdominal circumference (AC) < 3(rd) centile, estimated fetal weight (EFW) < 3(rd) centile and absent end-diastolic flow in the umbilical artery (UA)) and four contributory parameters (AC or EFW < 10(th) centile combined with a pulsatility index (PI) > 95(th) centile in either the UA or uterine artery) were agreed upon."
    explanation: >
      Fixes the < 32 week boundary for this subtype and records absent umbilical
      artery end-diastolic flow as a solitary diagnostic criterion for it.

- name: Late FGR
  display_name: Late-onset FGR (>= 32 weeks)
  description: >
    FGR diagnosed at or after 32 weeks' gestational age. It is the commoner but
    more subtle form, and is harder to detect. Its consensus definition drops
    absent end-diastolic flow as a solitary criterion and reaches instead for
    the cerebroplacental ratio or umbilical artery pulsatility index - a
    diagnostic shift that follows the mechanism, since the fetal
    cardiovascular-redistribution arm rather than frank umbilical-artery
    end-diastolic flow loss is what is measurable at this gestation.
  evidence:
  - reference: PMID:26909664
    reference_title: "Consensus definition of fetal growth restriction: a Delphi procedure."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For late FGR (≥ 32 weeks), two solitary parameters (AC or EFW < 3(rd) centile) and four contributory parameters (EFW or AC < 10(th) centile, AC or EFW crossing centiles by > two quartiles on growth charts and cerebroplacental ratio < 5(th) centile or UA-PI > 95(th) centile) were defined."
    explanation: >
      Fixes the >= 32 week boundary for this subtype and shows that its
      contributory parameters use the cerebroplacental ratio and UA-PI rather
      than absent end-diastolic flow.
  - reference: PMID:32965939
    reference_title: Fetal Growth Restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These parameters differed depending on whether FGR was early-onset FGR (<32 weeks gestational age) or late-onset FGR (≥32 weeks gestational age) based on gestational age at diagnosis"
    explanation: Confirms that the diagnostic parameters themselves differ by the early/late gestational-age split.

definitions:
- name: Delphi consensus definition of early and late FGR
  definition_type: DIAGNOSTIC_CRITERIA
  derivation_basis: ESTABLISHED_CRITERIA
  description: >
    The internationally used case definition separates early FGR (< 32 weeks)
    from late FGR (>= 32 weeks) and, for each, distinguishes solitary parameters
    that are sufficient on their own from contributory parameters that require a
    second abnormality. Its structure is itself a mechanistic statement: absent
    end-diastolic flow in the umbilical artery is accepted as a solitary
    criterion for early FGR, meaning the placental-vascular lesion can establish
    the diagnosis without any size criterion being met.
  evidence:
  - reference: PMID:26909664
    reference_title: "Consensus definition of fetal growth restriction: a Delphi procedure."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For early FGR (< 32 weeks), three solitary parameters (abdominal circumference (AC) < 3(rd) centile, estimated fetal weight (EFW) < 3(rd) centile and absent end-diastolic flow in the umbilical artery (UA)) and four contributory parameters (AC or EFW < 10(th) centile combined with a pulsatility index (PI) > 95(th) centile in either the UA or uterine artery) were agreed upon."
    explanation: >
      States the agreed solitary and contributory parameters for early FGR,
      including absent umbilical artery end-diastolic flow as a solitary
      criterion.
  - reference: PMID:26909664
    reference_title: "Consensus definition of fetal growth restriction: a Delphi procedure."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Consensus-based definitions for early and late FGR, as well as cut-off values for parameters involved, were agreed upon by a panel of experts."
    explanation: Establishes that the early/late split and its cut-offs are expert-consensus derived.
  notes: >
    Recorded as ESTABLISHED_CRITERIA rather than MECHANISTIC_HYPOTHESIS: this is
    a consensus case definition, not a case-finding query predicated on an
    unproven mechanism.

- name: Fetal growth restriction versus small for gestational age
  definition_type: DIAGNOSTIC_CRITERIA
  derivation_basis: ESTABLISHED_CRITERIA
  description: >
    SGA is a statistical threshold on size relative to a reference population;
    FGR is a claim about failed growth potential from a pathological cause. The
    two sets overlap but neither contains the other, and conflating them is the
    single most common source of misclassification in the FGR literature - it
    dilutes cohorts with healthy small fetuses and misses growth-restricted
    fetuses of normal size.
  evidence:
  - reference: PMID:33972065
    reference_title: "Abnormal Fetal Growth: Small for Gestational Age, Fetal Growth Restriction, Large for Gestational Age: Definitions and Epidemiology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fetuses can be constitutionally small or large and thus healthy, whereas fetuses with seemingly normal size can be growth restricted or overgrown."
    explanation: States directly that size thresholds and growth pathology are non-equivalent in both directions.
  - reference: PMID:33972065
    reference_title: "Abnormal Fetal Growth: Small for Gestational Age, Fetal Growth Restriction, Large for Gestational Age: Definitions and Epidemiology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, both are statistical definitions of fetal size below or above a certain threshold related to a reference population, rather than referring to an abnormal condition."
    explanation: Establishes that SGA/LGA are statistical rather than pathological categories.
  - reference: PMID:32965939
    reference_title: Fetal Growth Restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "FGR is generally defined as the failure of a fetus to achieve its full genetically determined growth potential due to pathologic etiologies, primarily placental dysfunction."
    explanation: Gives the potential-based definition of FGR and names placental dysfunction as the dominant cause.

clinical_burden:
  burden_level: HIGH
  rationale: >
    FGR is among the largest contributors to stillbirth and to neonatal death
    and morbidity worldwide, and the affected child carries elevated risk well
    beyond the neonatal period. Its burden is amplified by the absence of any
    in-utero treatment: the only lever available is deciding when to deliver a
    fetus that is deteriorating in utero but immature outside it.
  evidence:
  - reference: PMID:32965939
    reference_title: Fetal Growth Restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fetal growth restriction (FGR) is a common pregnancy complication worldwide, leading to stillbirth and neonatal mortality and morbidity."
    explanation: States the global frequency and the principal adverse outcomes.
  - reference: PMID:33085318
    reference_title: Placental Insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This condition accounts for a substantial proportion of global perinatal morbidity and mortality."
    explanation: Attributes a substantial share of global perinatal morbidity and mortality to the underlying placental insufficiency.

pathophysiology:
- name: Deficient Uterine Spiral Artery Remodeling
  conforms_to: "deep_placentation_defect#Failure of Spiral Artery Physiological Transformation"
  biological_scale: TISSUE
  description: >
    In normal pregnancy extravillous trophoblast invades the decidua and inner
    myometrium and converts the maternal spiral arteries into wide, flaccid,
    low-resistance conduits. When that conversion is deficient the arteries
    remain narrow and vasoreactive, and uteroplacental perfusion is fixed at an
    inadequate level from early pregnancy onward. This is the initiating lesion
    shared with preeclampsia and placental abruption.
  cell_types:
  - preferred_term: extravillous trophoblast
    term:
      id: CL:0008036
      label: extravillous trophoblast
  biological_processes:
  - preferred_term: maternal placenta development
    term:
      id: GO:0001893
      label: maternal placenta development
    modifier: DECREASED
  downstream:
  - target: Uteroplacental Malperfusion
    causal_link_type: DIRECT
    description: >
      Failure to convert the spiral arteries is what produces the malperfused
      intervillous space.
    evidence:
    - reference: PMID:29422210
      reference_title: Pathophysiology of placental-derived fetal growth restriction.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "deficient remodeling of the uterine spiral arteries supplying the placenta during early pregnancy. The resultant malperfusion"
      explanation: The word "resultant" makes malperfusion the direct consequence of the deficient spiral artery remodeling named in the preceding clause.
  evidence:
  - reference: PMID:29422210
    reference_title: Pathophysiology of placental-derived fetal growth restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Placental-related fetal growth restriction arises primarily due to deficient remodeling of the uterine spiral arteries supplying the placenta during early pregnancy."
    explanation: Establishes deficient spiral artery remodeling as the primary initiating lesion in placental FGR.

- name: Uteroplacental Malperfusion
  conforms_to: "deep_placentation_defect#High-Momentum, Intermittent Uteroplacental Perfusion"
  biological_scale: TISSUE
  description: >
    With the spiral arteries unconverted, perfusion of the intervillous space is
    inadequate from early pregnancy onward. This is a tissue-level perfusion
    failure of the uteroplacental unit - the haemodynamic state that the
    placental cells then have to respond to - and is the lesion that imaging of
    the intraplacental vasculature detects.
  notes: >
    The conformance target characterizes the inflow of an unconverted artery as
    high-momentum and intermittent rather than steady, and says that the
    distinction matters because repeated ischaemia-reperfusion and steady
    hypoxia produce different downstream cell-death phenotypes. The sources
    cited here (PMID:29422210, PMID:33085318) describe the deficit only as
    inadequate perfusion and do not resolve its time course in FGR, so this node
    asserts the inadequacy and leaves the momentum and intermittency claims to
    the module. An earlier wording called the rate "fixed", which asserted more
    than those sources say and read as a contradiction of the module node.
  downstream:
  - target: Placental Cell Stress Response
    causal_link_type: DIRECT
    description: >
      Malperfusion is what imposes cell stress on the placental tissues, and the
      stress response it induces is selective rather than indiscriminate.
    evidence:
    - reference: PMID:29422210
      reference_title: Pathophysiology of placental-derived fetal growth restriction.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The resultant malperfusion induces cell stress within the placental tissues, leading to selective suppression of protein synthesis and reduced cell proliferation."
      explanation: States that malperfusion induces the placental cell stress, and names the selective suppression that characterizes it.
  evidence:
  - reference: PMID:33085318
    reference_title: Placental Insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The disorder generally involves inadequate placental perfusion, which leads to insufficient delivery of oxygen and nutrients to the fetus."
    explanation: Names inadequate placental perfusion as the tissue-level perfusion failure at the centre of placental insufficiency.

- name: Placental Cell Stress Response
  conforms_to: "deep_placentation_defect#Syncytiotrophoblast Oxidative Stress and Apoptosis"
  biological_scale: CELLULAR
  description: >
    The malperfused placenta experiences oxidative and endoplasmic reticulum
    stress. The cellular response is not indiscriminate injury but a selective
    shutdown - protein synthesis is suppressed and proliferation falls - which
    is why the placenta becomes small and hypoplastic rather than simply
    necrotic. In more severe cases infarction and fibrin deposition are
    superimposed.
  cell_types:
  - preferred_term: syncytiotrophoblast
    term:
      id: CL:0000525
      label: syncytiotrophoblast cell
  biological_processes:
  - preferred_term: response to hypoxia
    term:
      id: GO:0001666
      label: response to hypoxia
    modifier: INCREASED
  - preferred_term: cytoplasmic translation
    term:
      id: GO:0002181
      label: cytoplasmic translation
    modifier: DECREASED
  - preferred_term: cell population proliferation
    term:
      id: GO:0008283
      label: cell population proliferation
    modifier: DECREASED
  notes: >
    Conformance to the module node is partial and deliberately so. The module
    node carries GO:0006915 apoptotic process INCREASED; that term is not added
    here because the source cited for this node (PMID:29422210) describes a
    selective shutdown - suppressed protein synthesis and reduced proliferation,
    giving a small hypoplastic placenta rather than a necrotic one - and does
    not report increased apoptosis. Adding the binding would assert a measured
    increase this entry cannot cite. The oxidative and ER stress half of the
    module node is what this node shares.
  downstream:
  - target: Reduced Villous Volume and Exchange Surface Area
    causal_link_type: DIRECT
    description: >
      Suppressed protein synthesis and proliferation, compounded by infarction
      and fibrin deposition, reduce the villous tissue available for exchange.
    evidence:
    - reference: PMID:29422210
      reference_title: Pathophysiology of placental-derived fetal growth restriction.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Consequently, there is a reduction in villous volume and surface area for maternal-fetal exchange."
      explanation: States the reduction in villous volume and exchange surface as the direct consequence of the preceding stress response.
  - target: Impaired Placental Nutrient Transport
    causal_link_type: DIRECT
    description: >
      Placental stress drives extensive dysregulation of imprinted and
      non-imprinted gene expression, which alters transport function
      specifically - a change in transporter capacity that is separate from the
      loss of surface area.
    evidence:
    - reference: PMID:29422210
      reference_title: Pathophysiology of placental-derived fetal growth restriction.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Extensive dysregulation of imprinted and nonimprinted gene expression occurs, affecting placental transport, endocrine, metabolic, and immune functions."
      explanation: Links the stressed placenta to dysregulated gene expression that specifically affects transport function.
  - target: Stem Villous Arterial Smooth Muscle Dedifferentiation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >
      The source calls the stem villous arterial change "secondary", placing it
      downstream of the placental disease process rather than alongside it, but
      does not name what it is secondary to or by what route. The edge is drawn
      so the fetal-side arm is not left hanging as an independent initiating
      lesion, and typed INDIRECT_UNKNOWN_INTERMEDIATES because the intervening
      steps are genuinely unstated.
    evidence:
    - reference: PMID:29422210
      reference_title: Pathophysiology of placental-derived fetal growth restriction.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Secondary changes involving dedifferentiation of smooth muscle cells surrounding the fetal arteries within placental stem villi correlate with absent or reversed end-diastolic umbilical artery blood flow, and with a reduction in birthweight."
      explanation: >
        The word "Secondary" is the whole basis for the ordering, which is why
        this is PARTIAL - the source establishes that the change is downstream
        of the placental process without identifying the mechanism connecting
        them.
  evidence:
  - reference: PMID:29422210
    reference_title: Pathophysiology of placental-derived fetal growth restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These effects are compounded in more severe cases by increased infarction and fibrin deposition."
    explanation: Records the superimposed infarction and fibrin deposition seen in severe disease.

- name: Reduced Villous Volume and Exchange Surface Area
  biological_scale: TISSUE
  description: >
    The structural endpoint of placental stress is a smaller placenta with less
    villous tissue and less surface area across which maternal-fetal exchange
    can occur. This is the anatomical substrate of placental insufficiency, and
    is what the histopathological pattern of distal villous hypoplasia
    describes.
  biological_processes:
  - preferred_term: placenta blood vessel development
    term:
      id: GO:0060674
      label: placenta blood vessel development
    modifier: DECREASED
  downstream:
  - target: Chronic Fetal Hypoxemia and Nutrient Deprivation
    causal_link_type: DIRECT
    description: >
      Reduced exchange capacity is what limits delivery of oxygen and substrate
      to the fetus.
    evidence:
    - reference: PMID:33085318
      reference_title: Placental Insufficiency.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The disorder generally involves inadequate placental perfusion, which leads to insufficient delivery of oxygen and nutrients to the fetus."
      explanation: States the step from inadequate placental perfusion to insufficient fetal oxygen and nutrient delivery.
  evidence:
  - reference: PMID:29422210
    reference_title: Pathophysiology of placental-derived fetal growth restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Consequently, there is a reduction in villous volume and surface area for maternal-fetal exchange."
    explanation: Directly states the reduction in villous volume and exchange surface area.

- name: Impaired Placental Nutrient Transport
  biological_scale: MOLECULAR
  description: >
    Independently of how much surface area remains, the transporters themselves
    carry less. System A amino acid transporter activity is reduced in placentas
    from growth-restricted pregnancies, and the affected infants have lower
    circulating amino acid concentrations. The imprinted Igf2-H19 locus is a
    principal regulator of this supply-demand matching, which is why imprinted
    gene dysregulation translates into a nutrient-transfer deficit.
  biological_processes:
  - preferred_term: amino acid transmembrane transport
    term:
      id: GO:0003333
      label: amino acid transmembrane transport
    modifier: DECREASED
  downstream:
  - target: Chronic Fetal Hypoxemia and Nutrient Deprivation
    causal_link_type: DIRECT
    description: >
      Reduced placental amino acid transport lowers the substrate actually
      reaching the fetal circulation.
    evidence:
    - reference: PMID:18718657
      reference_title: "Placental system A amino acid transport is reduced in pregnancies with small for gestational age (SGA) infants but not in preeclampsia with SGA infants."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Infants with IUGR have decreased concentrations of amino acids in their blood and system A amino acid transporter activity is reduced in their placentas."
      explanation: Pairs the reduced placental transporter activity with the corresponding deficit in fetal circulating amino acids.
  evidence:
  - reference: PMID:18718657
    reference_title: "Placental system A amino acid transport is reduced in pregnancies with small for gestational age (SGA) infants but not in preeclampsia with SGA infants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We confirm the reduced uptake of amino acids in SGA pregnancies without preeclampsia but report that placental amino acid uptake of SGA infants with maternal preeclampsia is not reduced"
    explanation: >
      Confirms reduced system A uptake in SGA without preeclampsia, and is
      curated deliberately with its negative half intact - the transport deficit
      was NOT found when the same growth restriction occurred alongside
      preeclampsia, so reduced amino acid transport cannot be assumed to be a
      universal feature of every growth-restricted placenta.
  - reference: PMID:16612114
    reference_title: "Imprinted genes, placental development and fetal growth."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "They affect the growth, morphology and nutrient transfer capacity of the placenta and, thereby, control the nutrient supply for fetal growth."
    explanation: >
      Places imprinted genes upstream of placental nutrient transfer capacity.
      Tagged MODEL_ORGANISM because the mechanistic dissection cited is the
      murine Igf2P0 and Igf2-null comparison.

- name: Chronic Fetal Hypoxemia and Nutrient Deprivation
  biological_scale: ORGANISM
  description: >
    The fetal-compartment consequence of placental insufficiency: a sustained,
    progressive shortfall of oxygen and substrate. It is chronic rather than
    acute, which is what allows the adaptive responses below to develop and what
    distinguishes the FGR trajectory from an acute event such as abruption.
  biological_processes:
  - preferred_term: response to hypoxia
    term:
      id: GO:0001666
      label: response to hypoxia
    modifier: INCREASED
  downstream:
  - target: Fetal Cardiovascular Redistribution (Brain Sparing)
    causal_link_type: DIRECT
    description: >
      Hypoxaemia is the direct trigger for redistribution of fetal cardiac
      output toward the brain and other vital organs.
    evidence:
    - reference: PMID:33085318
      reference_title: Placental Insufficiency.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Physiologically, hypoxemia triggers adaptive fetal responses, including redistribution of blood flow toward vital organs (brain sparing), diminished fetal movement, and reduced somatic growth."
      explanation: Names hypoxemia as the trigger and brain sparing as the adaptive response.
  - target: Failure to Achieve Genetically Determined Growth Potential
    causal_link_type: DIRECT
    description: >
      Substrate shortfall directly limits somatic growth, which is the defining
      manifestation of the disease.
    evidence:
    - reference: PMID:33085318
      reference_title: Placental Insufficiency.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Physiologically, hypoxemia triggers adaptive fetal responses, including redistribution of blood flow toward vital organs (brain sparing), diminished fetal movement, and reduced somatic growth."
      explanation: Lists reduced somatic growth among the direct fetal responses to hypoxemia.
  evidence:
  - reference: PMID:33085318
    reference_title: Placental Insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Current understanding characterizes the condition as a progressive decline in placental function that culminates in chronic fetal hypoxemia, metabolic acidosis, and FGR."
    explanation: States the progressive placental decline culminating in chronic fetal hypoxemia.

- name: Fetal Cardiovascular Redistribution (Brain Sparing)
  biological_scale: ORGANISM
  description: >
    The hypoxaemic fetus preferentially perfuses brain, myocardium and adrenals
    at the expense of the splanchnic bed, kidneys, skeleton and muscle. The
    clinical corollary matters: brain sparing is measured as a fall in the
    cerebroplacental ratio and is the reason growth restriction is often
    asymmetric, with abdominal circumference falling away before head
    circumference. It is a marker of successful compensation, not of a fetus
    that is safe.
  downstream:
  - target: Failure to Achieve Genetically Determined Growth Potential
    causal_link_type: DIRECT
    description: >
      Diverting cardiac output away from the splanchnic and musculoskeletal beds
      is part of why somatic growth stops, and why the restriction is typically
      asymmetric.
    evidence:
    - reference: PMID:33085318
      reference_title: Placental Insufficiency.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Physiologically, hypoxemia triggers adaptive fetal responses, including redistribution of blood flow toward vital organs (brain sparing), diminished fetal movement, and reduced somatic growth."
      explanation: Groups redistribution and reduced somatic growth as parts of the same adaptive response.
  evidence:
  - reference: PMID:33085318
    reference_title: Placental Insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physiologically, hypoxemia triggers adaptive fetal responses, including redistribution of blood flow toward vital organs (brain sparing), diminished fetal movement, and reduced somatic growth."
    explanation: Directly describes brain sparing as redistribution of blood flow toward vital organs.

- name: Stem Villous Arterial Smooth Muscle Dedifferentiation
  biological_scale: TISSUE
  description: >
    A change on the fetal side of the placenta, distinct from the maternal
    spiral artery lesion that started the disease. Smooth muscle cells
    surrounding the fetal arteries within the placental stem villi
    dedifferentiate, and this correlates with the umbilical artery Doppler
    abnormality used clinically to grade severity. Curating it as its own node
    is what makes absent/reversed end-diastolic flow a mechanistic readout of
    placental vascular pathology rather than an unexplained imaging sign.
  cell_types:
  - preferred_term: placental stem villous arterial smooth muscle cell
    term:
      id: CL:0009093
      label: smooth muscle cell of placenta
  downstream:
  - target: Absent or Reversed Umbilical Artery End-Diastolic Flow
    causal_link_type: DIRECT
    description: >
      Dedifferentiation of the smooth muscle around the fetal stem villous
      arteries is the correlate of the abnormal umbilical artery waveform. Note
      the source claims correlation, not demonstrated causation - see the linked
      knowledge gap.
    evidence:
    - reference: PMID:29422210
      reference_title: Pathophysiology of placental-derived fetal growth restriction.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Secondary changes involving dedifferentiation of smooth muscle cells surrounding the fetal arteries within placental stem villi correlate with absent or reversed end-diastolic umbilical artery blood flow, and with a reduction in birthweight."
      explanation: >
        States the correlation between stem villous smooth muscle
        dedifferentiation and absent/reversed end-diastolic umbilical artery
        flow. Marked PARTIAL because the source asserts correlation only.
  evidence:
  - reference: PMID:29422210
    reference_title: Pathophysiology of placental-derived fetal growth restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Secondary changes involving dedifferentiation of smooth muscle cells surrounding the fetal arteries within placental stem villi correlate with absent or reversed end-diastolic umbilical artery blood flow, and with a reduction in birthweight."
    explanation: Establishes the fetal stem villous arterial change and its correlation with birthweight reduction.

- name: Absent or Reversed Umbilical Artery End-Diastolic Flow
  biological_scale: ORGANISM
  description: >
    Rising placental vascular resistance first blunts, then abolishes, and
    finally reverses diastolic flow in the umbilical artery. This is the
    principal surveillance axis in early FGR and, in the consensus case
    definition, absent end-diastolic flow is on its own sufficient to diagnose
    early FGR without any size criterion.
  downstream:
  - target: Fetal Metabolic Acidosis and Decompensation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >
      Deterioration of the umbilical artery waveform marks progression toward
      metabolic acidosis, but the ordering and the intervening steps between
      Doppler deterioration and acidaemia are inferred from surveillance
      sequences rather than from a demonstrated mechanism.
    evidence:
    - reference: PMID:33085318
      reference_title: Placental Insufficiency.
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: HUMAN_CLINICAL
      snippet: "Current understanding characterizes the condition as a progressive decline in placental function that culminates in chronic fetal hypoxemia, metabolic acidosis, and FGR."
      explanation: >
        Supports progressive placental decline ending in metabolic acidosis.
        Marked INDIRECT because it describes the overall trajectory without
        establishing the umbilical artery waveform as the specific antecedent
        step.
  evidence:
  - reference: PMID:26909664
    reference_title: "Consensus definition of fetal growth restriction: a Delphi procedure."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For early FGR (< 32 weeks), three solitary parameters (abdominal circumference (AC) < 3(rd) centile, estimated fetal weight (EFW) < 3(rd) centile and absent end-diastolic flow in the umbilical artery (UA)) and four contributory parameters (AC or EFW < 10(th) centile combined with a pulsatility index (PI) > 95(th) centile in either the UA or uterine artery) were agreed upon."
    explanation: Records absent umbilical artery end-diastolic flow as a solitary diagnostic criterion for early FGR.

- name: Failure to Achieve Genetically Determined Growth Potential
  biological_scale: ORGANISM
  description: >
    The defining manifestation. Framed as failure against the fetus's own
    potential rather than against a population centile, which is what separates
    FGR from constitutional smallness.
  downstream:
  - target: Fetal Metabolic Acidosis and Decompensation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >
      Continuing placental decline in an already growth-restricted fetus
      progresses to acidaemia; the growth deficit itself is a marker of the
      severity of the supply failure rather than a cause of the acidosis.
    evidence:
    - reference: PMID:33085318
      reference_title: Placental Insufficiency.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Current understanding characterizes the condition as a progressive decline in placental function that culminates in chronic fetal hypoxemia, metabolic acidosis, and FGR."
      explanation: >
        Places FGR and metabolic acidosis on the same progressive trajectory.
        PARTIAL because it does not order them causally.
  evidence:
  - reference: PMID:32965939
    reference_title: Fetal Growth Restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "FGR is generally defined as the failure of a fetus to achieve its full genetically determined growth potential due to pathologic etiologies, primarily placental dysfunction."
    explanation: Defines the node in the terms used by the field.

- name: Fetal Metabolic Acidosis and Decompensation
  biological_scale: ORGANISM
  description: >
    The terminal step, in which compensation fails: oxygen delivery falls below
    what anaerobic metabolism can offset, lactate accumulates and the fetus
    becomes acidaemic. It is the event that the entire surveillance apparatus
    exists to anticipate, because its endpoint is stillbirth and the only
    available intervention - delivery - must be taken before it occurs.
  evidence:
  - reference: PMID:33085318
    reference_title: Placental Insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Current understanding characterizes the condition as a progressive decline in placental function that culminates in chronic fetal hypoxemia, metabolic acidosis, and FGR."
    explanation: Names metabolic acidosis as the culmination of progressive placental decline.
  - reference: PMID:32965939
    reference_title: Fetal Growth Restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fetal growth restriction (FGR) is a common pregnancy complication worldwide, leading to stillbirth and neonatal mortality and morbidity."
    explanation: Records stillbirth and neonatal death as the outcomes of the decompensated state.

phenotypes:
- category: Fetal
  name: Failure of Fetal Growth
  description: >
    Estimated fetal weight or abdominal circumference below the expected
    centile, or falling across centiles on serial measurement. The HPO term is
    the closest available match; note it is expressed in the older "growth
    retardation" vocabulary that the field has moved away from.
  phenotype_term:
    preferred_term: Fetal growth restriction
    term:
      id: HP:0001511
      label: Intrauterine growth retardation
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:32965939
    reference_title: Fetal Growth Restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "FGR is generally defined as the failure of a fetus to achieve its full genetically determined growth potential due to pathologic etiologies, primarily placental dysfunction."
    explanation: The defining phenotype of the entry.

- category: Fetal
  name: Absent End-Diastolic Umbilical Artery Flow
  description: >
    Loss of forward flow in the umbilical artery during diastole, reflecting
    high placental vascular resistance. A solitary diagnostic criterion for
    early FGR.
  phenotype_term:
    preferred_term: Absent end-diastolic umbilical artery flow
    term:
      id: HP:0034224
      label: Absent end-diastolic umbilical artery flow
  evidence:
  - reference: PMID:26909664
    reference_title: "Consensus definition of fetal growth restriction: a Delphi procedure."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For early FGR (< 32 weeks), three solitary parameters (abdominal circumference (AC) < 3(rd) centile, estimated fetal weight (EFW) < 3(rd) centile and absent end-diastolic flow in the umbilical artery (UA)) and four contributory parameters (AC or EFW < 10(th) centile combined with a pulsatility index (PI) > 95(th) centile in either the UA or uterine artery) were agreed upon."
    explanation: Lists absent umbilical artery end-diastolic flow as a solitary criterion.

- category: Fetal
  name: Abnormal Umbilical Artery Doppler Waveform
  description: >
    Raised umbilical artery pulsatility index (> 95th centile) is the
    contributory Doppler criterion, and the earlier abnormality on the same axis
    that precedes loss of end-diastolic flow.
  phenotype_term:
    preferred_term: Elevated umbilical artery pulsatility index
    term:
      id: HP:0025715
      label: Abnormal umbilical artery doppler waveform during pregnancy
  evidence:
  - reference: PMID:25747582
    reference_title: "2 year neurodevelopmental and intermediate perinatal outcomes in infants with very preterm fetal growth restriction (TRUFFLE): a randomised trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "high umbilical artery Doppler pulsatility index"
    explanation: Uses raised umbilical artery pulsatility index as a trial entry criterion defining very preterm FGR.

- category: Fetal
  name: Decreased Fetal Movement
  description: >
    Reduced fetal activity is part of the adaptive response to hypoxaemia,
    conserving oxygen consumption, and is a common presenting complaint.
  phenotype_term:
    preferred_term: Decreased fetal movement
    term:
      id: HP:0001558
      label: Decreased fetal movement
  evidence:
  - reference: PMID:33085318
    reference_title: Placental Insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physiologically, hypoxemia triggers adaptive fetal responses, including redistribution of blood flow toward vital organs (brain sparing), diminished fetal movement, and reduced somatic growth."
    explanation: Lists diminished fetal movement among the adaptive responses to hypoxemia.

- category: Fetal
  name: Oligohydramnios
  description: >
    Redistribution away from the fetal kidneys reduces urine output and
    therefore amniotic fluid volume; oligohydramnios is a recognised
    manifestation of the same placental insufficiency.
  phenotype_term:
    preferred_term: Oligohydramnios
    term:
      id: HP:0001562
      label: Oligohydramnios
  evidence:
  - reference: PMID:33085318
    reference_title: Placental Insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Placental insufficiency, also known as uteroplacental insufficiency, contributes to a broad spectrum of obstetric complications, including preeclampsia, fetal growth restriction (FGR), oligohydramnios, and stillbirth."
    explanation: Lists oligohydramnios among the complications of placental insufficiency.

- category: Fetal
  name: Fetal Distress
  description: >
    Non-reassuring fetal status, including reduced cardiotocograph short-term
    variation, marks the transition from compensated to decompensating disease
    and is one of the triggers for delivery.
  phenotype_term:
    preferred_term: Fetal distress
    term:
      id: HP:0025116
      label: Fetal distress
  evidence:
  - reference: PMID:25747582
    reference_title: "2 year neurodevelopmental and intermediate perinatal outcomes in infants with very preterm fetal growth restriction (TRUFFLE): a randomised trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We aimed to assess whether changes in the fetal ductus venosus Doppler waveform (DV) could be used as indications for delivery instead of cardiotocography short-term variation (STV)."
    explanation: Establishes reduced cardiotocograph short-term variation as the comparator indication for delivery, i.e. the standard marker of fetal compromise.

- category: Neonatal
  name: Preterm Birth
  description: >
    Most severe early-onset FGR ends in medically indicated preterm delivery,
    so prematurity and its complications are intrinsic to the disease course
    rather than incidental. In TRUFFLE the median gestational age at delivery
    was under 31 weeks.
  phenotype_term:
    preferred_term: Premature birth
    term:
      id: HP:0001622
      label: Premature birth
  evidence:
  - reference: PMID:25747582
    reference_title: "2 year neurodevelopmental and intermediate perinatal outcomes in infants with very preterm fetal growth restriction (TRUFFLE): a randomised trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The median gestational age at delivery was 30"
    explanation: >
      Quantifies gestational age at delivery in a severe early-onset FGR trial
      cohort. The quote is truncated before the decimal separator because the
      source renders it with a middle dot.

- category: Neonatal
  name: Neonatal Hypoglycemia
  description: >
    The growth-restricted newborn has depleted hepatic glycogen and minimal
    adipose reserve, so glucose homeostasis fails once the placental supply is
    withdrawn at birth.
  phenotype_term:
    preferred_term: Neonatal hypoglycemia
    term:
      id: HP:0001943
      label: Hypoglycemia
    temporality: TRANSIENT
  notes: >
    No evidence item is attached. This is standard neonatal teaching, but none
    of the references cached for this entry states it in a form that can be
    quoted as an exact snippet, and fabricating one would violate the evidence
    SOP. Recorded per the SOP's option of keeping the description without an
    evidence block.

- category: Neonatal
  name: Polycythemia
  description: >
    Chronic fetal hypoxaemia drives erythropoietin-mediated increased red cell
    production, so the growth-restricted neonate is frequently polycythaemic.
  phenotype_term:
    preferred_term: Polycythemia
    term:
      id: HP:0001901
      label: Polycythemia
  notes: >
    No evidence item attached, for the same reason as the hypoglycaemia
    phenotype above.

- category: Fetal
  name: Stillbirth
  description: >
    Intrauterine fetal death is the outcome that FGR surveillance exists to
    prevent, and FGR is among the largest attributable causes of stillbirth
    worldwide.
  evidence:
  - reference: PMID:32965939
    reference_title: Fetal Growth Restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fetal growth restriction (FGR) is a common pregnancy complication worldwide, leading to stillbirth and neonatal mortality and morbidity."
    explanation: States stillbirth as a leading outcome of FGR.
  notes: >
    Deliberately left without a phenotype_term. The correct HPO term,
    HP:0003826 Stillbirth, sits under Clinical modifier / Clinical course
    (HP:0031797) rather than under Phenotypic abnormality (HP:0000118), and the
    PhenotypeTerm dynamic enum is rooted at HP:0000118, so the term cannot be
    bound here without failing validation. Verified with
    `runoak -i sqlite:obo:hp ancestors -p i,p HP:0003826`. Binding a different,
    wrong term or dropping the phenotype would both be worse than leaving it
    unbound with this note. This is the fourth dismech entry to hit the same
    structural gap - see issue #7837 gap 3, plus
    Familial_Hyperaldosteronism_Type_I (HP:0100602),
    Intrahepatic_Cholestasis_of_Pregnancy and
    Hemolytic_Disease_of_the_Fetus_and_Newborn (both stillbirth).

- category: Childhood
  name: Adverse Neurodevelopmental Outcome
  description: >
    Survivors of severe early-onset FGR carry a substantial risk of cerebral
    palsy, neurosensory impairment or developmental delay, which is why the
    randomised trials in this disease use a 2-year neurodevelopmental composite
    rather than birthweight as their primary endpoint.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:25747582
    reference_title: "2 year neurodevelopmental and intermediate perinatal outcomes in infants with very preterm fetal growth restriction (TRUFFLE): a randomised trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The primary outcome was survival without cerebral palsy or neurosensory impairment, or a Bayley III developmental score of less than 85, at 2 years of age."
    explanation: Defines the composite neurodevelopmental outcome used as the trial primary endpoint in severe FGR.
  - reference: PMID:30169244
    reference_title: "Maternal sildenafil for severe fetal growth restriction (STRIDER): a multicentre, randomised, placebo-controlled, double-blind trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Severe early-onset fetal growth restriction can lead to a range of adverse outcomes including fetal or neonatal death, neurodisability, and lifelong risks to the health of the affected child."
    explanation: States neurodisability and lifelong health risk among the outcomes of severe early-onset FGR.

histopathology:
- name: Maternal Vascular Malperfusion
  description: >
    The consensus placental-pathology diagnosis corresponding to the maternal
    spiral artery lesion. The Amsterdam Placental Workshop Group statement is
    what standardised this terminology; before it, laboratories used
    incompatible definitions, which is a large part of why the older
    clinicopathological literature on FGR is hard to compare.
  evidence:
  - reference: PMID:27223167
    reference_title: "Sampling and Definitions of Placental Lesions: Amsterdam Placental Workshop Group Consensus Statement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The terminology and microscopic descriptions for maternal vascular malperfusion, fetal vascular malperfusion, delayed villous maturation, patterns of ascending intrauterine infection, and villitis of unknown etiology were agreed upon."
    explanation: Establishes maternal vascular malperfusion as a consensus-defined placental lesion category.
  - reference: PMID:27223167
    reference_title: "Sampling and Definitions of Placental Lesions: Amsterdam Placental Workshop Group Consensus Statement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The value of placental examination in investigations of adverse pregnancy outcomes may be compromised by sampling and definition differences between laboratories."
    explanation: Records why the standardisation was needed, and hence the comparability caveat on older literature.

- name: Distal Villous Hypoplasia and Increased Syncytial Knots
  description: >
    The microscopic correlate of reduced villous volume and exchange surface
    area - sparse, thin distal villi with increased syncytial knotting,
    accompanied by infarction and fibrin deposition.
  evidence:
  - reference: PMID:33085318
    reference_title: Placental Insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Histopathologic patterns commonly linked to placental insufficiency include distal villous hypoplasia, increased syncytial knots, maternal vascular malperfusion, placental infarctions, and fibrin deposition."
    explanation: Enumerates the histopathological pattern associated with placental insufficiency.
  - reference: PMID:29422210
    reference_title: Pathophysiology of placental-derived fetal growth restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These effects are compounded in more severe cases by increased infarction and fibrin deposition."
    explanation: Confirms infarction and fibrin deposition as severity-associated findings.

- name: Placental Lesions in FGR with Preeclampsia
  description: >
    Growth restriction accompanied by preeclampsia shows more severe placental
    damage than growth restriction alone. This is a useful piece of evidence for
    the two-outcome model: the same initiating lesion, at a higher level of
    placental stress, additionally produces the maternal syndrome.
  evidence:
  - reference: PMID:29422210
    reference_title: Pathophysiology of placental-derived fetal growth restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The changes are more severe in cases of growth restriction associated with preeclampsia compared to those with growth restriction alone, consistent with the greater degree of maternal vasculopathy reported in the former and more extensive macroscopic placental damage including infarcts, extensive fibrin deposition and microscopic villous developmental defects, atherosis of the spiral arteries, and noninfectious villitis."
    explanation: Directly contrasts placental lesion severity between FGR with and without preeclampsia.
  - reference: PMID:29422210
    reference_title: Pathophysiology of placental-derived fetal growth restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The higher level of stress may activate proinflammatory and apoptotic pathways within the syncytiotrophoblast, releasing factors that cause the maternal endothelial cell activation that distinguishes between the 2 conditions."
    explanation: >
      Gives the proposed mechanism by which the shared lesion diverges into FGR
      alone versus FGR with preeclampsia. Marked PARTIAL to match the source's
      own hedge - "may activate" - which is why this is curated as
      histopathological interpretation rather than as an asserted causal edge.

diagnosis:
- name: Ultrasound Biometry with Doppler Velocimetry
  description: >
    Diagnosis rests on serial ultrasound estimation of fetal weight and
    abdominal circumference against gestational-age references, combined with
    umbilical, uterine and middle cerebral artery Doppler. The Doppler component
    is not merely confirmatory - it carries diagnostic weight of its own in the
    consensus definition, and it is the axis on which severity and timing
    decisions are made.
  evidence:
  - reference: PMID:26909664
    reference_title: "Consensus definition of fetal growth restriction: a Delphi procedure."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "two solitary parameters (AC or EFW < 3(rd) centile) and four contributory parameters (EFW or AC < 10(th) centile, AC or EFW crossing centiles by > two quartiles on growth charts and cerebroplacental ratio < 5(th) centile or UA-PI > 95(th) centile) were defined."
    explanation: Sets out the biometric and Doppler parameters for diagnosing late FGR, including centile crossing and cerebroplacental ratio.

- name: Absence of a Pathognomonic Marker
  description: >
    There is no single test that establishes placental insufficiency. Diagnosis
    is a composite judgement from biometry, Doppler and growth trajectory, and
    the lack of a definitive marker is itself a documented obstacle to uniform
    diagnosis and to comparability between studies.
  evidence:
  - reference: PMID:33085318
    reference_title: Placental Insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recent evidence underscores the lack of a pathognomonic clinical or histologic marker, creating challenges in achieving uniform diagnosis and study of placental insufficiency."
    explanation: States the absence of a pathognomonic marker and its consequences for diagnosis and research.
  - reference: PMID:33085318
    reference_title: Placental Insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Despite extensive research, no universally accepted definition has been established."
    explanation: Records that even the definition of the underlying placental insufficiency remains unsettled.

environmental:
- name: Placental micro- and nanoplastic accumulation
  exposure_term:
    preferred_term: exposure to microplastic particle
    term:
      id: ECTO:7000061
      label: exposure to microplastic particle
  description: >-
    Micro- and nanoplastic particles reach the maternal-fetal interface, and
    with sensitive analytical methods they are recovered from essentially every
    human placenta examined. That the exposure occurs is settled; that it
    restricts fetal growth is not. The human evidence is a small case-control
    series in which placentas were sampled at delivery, so it cannot separate an
    effect of the particles from preferential accumulation in an
    already-failing, malperfused placenta - and the authors themselves report a
    non-monotonic dose-response. The mechanistic case comes from rodent
    gestational-exposure experiments at doses well above documented human tissue
    burdens. This entry is curated as a plausible but unproven exposure, and the
    causal edges below are graded to that standard rather than to the strength
    of the detection studies.
  evidence:
  - reference: PMID:38366932
    reference_title: Quantitation and identification of microplastics accumulation in human placental specimens using pyrolysis gas chromatography mass spectrometry.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "microplastics were present in all participants' placentae, with concentrations ranging widely from 6.5 to 685 µg NMPs per gram of placental tissue"
    explanation: >-
      Quantifies the plastic burden of human placental tissue and shows it is
      universal in the sampled cohort, which is the premise for treating
      placental microplastics as an exposure at this interface at all.
  - reference: PMID:33395930
    reference_title: "Plasticenta: First evidence of microplastics in human placenta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "12 microplastic fragments (ranging from 5 to 10 μm in size), with spheric or irregular shape were found in 4 placentas (5 in the fetal side, 4 in the maternal side and 3 in the chorioamniotic membranes)"
    explanation: >-
      The first demonstration that particles cross to the fetal side and the
      chorioamniotic membranes, not only the maternal surface, establishing that
      the fetal compartment is reached.
  influences_mechanisms:
  - target: Failure to Achieve Genetically Determined Growth Potential
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Placental microplastic count correlates inversely with birth weight and
      other neonatal anthropometry among growth-restricted pregnancies. The edge
      is drawn to the growth-failure node rather than to a placental mechanism
      because no intermediate step was measured. Direction of causation is
      unresolved: placentas were collected at delivery, particles were near or
      below the detection limit in almost all normal pregnancies, and a small
      dysfunctional placenta may concentrate or retain particles differently
      from a healthy one. Treat this as a signal worth testing prospectively,
      not as an established cause of FGR.
    evidence:
    - reference: PMID:36113646
      reference_title: Placental plastics in young women from general population correlate with reduced foetal growth in IUGR pregnancies.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "MPs were found in all (13 out of 13) intrauterine growth restriction (IUGR) pregnancies and their average abundance ranged from 2 to 38 particles per placenta, but were less than limit of detection (LOD) in normal pregnancies except three out of 30 subjects"
      explanation: >-
        Reports the case-control contrast the edge rests on. PARTIAL because it
        is cross-sectional with 13 IUGR placentas and establishes co-occurrence
        rather than a direction of effect.
    - reference: PMID:36113646
      reference_title: Placental plastics in young women from general population correlate with reduced foetal growth in IUGR pregnancies.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Inverse associations between MPs exposure and birth outcomes were observed in terms of birth weight (r = - 0.82, p < 0.001), length (r = - 0.56, p < 0.001), head circumference (r = - 0.50, p = 0.001), and 1-min Apgar score (r = - 0.75, p < 0.001) among those with IUGR"
      explanation: >-
        Quantifies the dose-response with the growth outcome this node names.
        PARTIAL for the same reason, and because the same paper reports the
        relationship is non-monotonic.
  - target: Placental Cell Stress Response
    environmental_effect: TRIGGERS
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      In gestationally exposed mice, polystyrene nanoplastics deplete placental
      nicotinamide and NAD+, which lowers ATP production and drives oxidative
      stress and ferroptosis - the same oxidative and energetic failure this
      node describes, but reached without malperfusion upstream. Rescue by
      nicotinamide supplementation and reproduction of the placental injury by
      faecal transfer from exposed dams make the chain interventional rather
      than merely correlative. It remains a rodent result at doses above
      measured human placental burdens; see the human-model mismatch discussion.
    evidence:
    - reference: PMID:40796882
      reference_title: Gut microbiota contributes to polystyrene nanoplastics-induced fetal growth restriction by disturbing placental nicotinamide metabolism.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "PS-NPs exposure observably reduced the levels of nicotinamide (NAM) and nicotinamide adenine dinucleotide (NAD+) in the placenta, resulting in decreased ATP production, increased oxidative stress and ferroptosis"
      explanation: >-
        Names the intermediates - NAM/NAD+ depletion, ATP loss, oxidative stress
        - that make this an indirect edge with known steps into the placental
        stress node.
    - reference: PMID:40796882
      reference_title: Gut microbiota contributes to polystyrene nanoplastics-induced fetal growth restriction by disturbing placental nicotinamide metabolism.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Treatment with NAM effectively mitigated disruptions in placental metabolism and reversed the adverse pregnancy outcomes caused by PS-NPs"
      explanation: >-
        A rescue experiment: restoring the depleted intermediate reverses the
        outcome, which is what distinguishes this from an observed association.
treatments:
- name: Doppler and Cardiotocograph Surveillance with Timed Delivery
  description: >
    The definitive management of FGR is not treatment of the fetus or placenta
    but surveillance and a decision about when to deliver, balancing the risk of
    continued intrauterine deterioration against the risk of prematurity. The
    TRUFFLE trial tested which surveillance signal should trigger delivery in
    very preterm FGR and found that using late ductus venosus changes was
    associated with better 2-year neurodevelopmental outcomes among survivors,
    though with a non-significant increase in mortality - a trade-off that the
    entry records rather than resolves.
  treatment_term:
    preferred_term: Therapeutic Procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  therapeutic_modality: OTHER
  target_mechanisms:
  - target: Fetal Metabolic Acidosis and Decompensation
    treatment_effect: INHIBITS
    description: >
      Delivery removes the fetus from the failing placental supply before
      acidosis and death occur. It does not act on any upstream node - it
      truncates the trajectory, which is why the effect is recorded against the
      terminal node rather than against the placental lesion.
    evidence:
    - reference: PMID:25747582
      reference_title: "2 year neurodevelopmental and intermediate perinatal outcomes in infants with very preterm fetal growth restriction (TRUFFLE): a randomised trial."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "No consensus exists for the best way to monitor and when to trigger delivery in mothers of babies with fetal growth restriction."
      explanation: Frames timing of delivery as the intervention lever, and records that the optimal trigger was unsettled.
  evidence:
  - reference: PMID:25747582
    reference_title: "2 year neurodevelopmental and intermediate perinatal outcomes in infants with very preterm fetal growth restriction (TRUFFLE): a randomised trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "late changes in the DV waveform might produce an improvement in developmental outcomes at 2 years of age."
    explanation: >
      Reports the trial's interpretation. Marked PARTIAL, matching the authors'
      own hedging: the primary endpoint difference was non-significant, and the
      favourable survivor outcome came with a non-significant increase in
      mortality.
  - reference: PMID:25747582
    reference_title: "2 year neurodevelopmental and intermediate perinatal outcomes in infants with very preterm fetal growth restriction (TRUFFLE): a randomised trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although the difference in the proportion of infants surviving without neuroimpairment was non-significant at the primary endpoint"
    explanation: Records the non-significant primary endpoint explicitly, so the entry does not overstate the trial result.

- name: Maternal Sildenafil
  description: >
    A mechanistically motivated attempt to treat the placental lesion itself:
    phosphodiesterase-5 inhibition potentiates nitric oxide and was expected to
    vasodilate the uterine vessels and improve fetal growth. It did not work.
    The STRIDER trial found no effect on any outcome, and the drug should not be
    used for this indication. It is curated here because a well-reasoned
    negative is a real constraint on the mechanism - it is evidence that late
    pharmacological vasodilatation cannot reverse an established
    early-pregnancy remodelling failure.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: sildenafil
      term:
        id: CHEBI:9139
        label: sildenafil
  therapeutic_modality: SMALL_MOLECULE
  evidence:
  - reference: PMID:30169244
    reference_title: "Maternal sildenafil for severe fetal growth restriction (STRIDER): a multicentre, randomised, placebo-controlled, double-blind trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sildenafil, a phosphodiesterase type 5 inhibitor, potentiates the actions of nitric oxide, which leads to vasodilatation of the uterine vessels and might improve fetal growth in utero."
    explanation: States the mechanistic rationale that motivated the trial.
  - reference: PMID:30169244
    reference_title: "Maternal sildenafil for severe fetal growth restriction (STRIDER): a multicentre, randomised, placebo-controlled, double-blind trial."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Sildenafil did not prolong pregnancy or improve pregnancy outcomes in severe early-onset fetal growth restriction and therefore it should not be prescribed for this indication outside of research studies with explicit participants' consent."
    explanation: Refutes benefit and issues an explicit recommendation against use for this indication.
  - reference: PMID:30169244
    reference_title: "Maternal sildenafil for severe fetal growth restriction (STRIDER): a multicentre, randomised, placebo-controlled, double-blind trial."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "and birthweight (-14 g,-100 to 126; p=0"
    explanation: >
      Gives the null birthweight effect estimate. The quote is truncated before
      the p-value's decimal separator because the source renders it with a
      middle dot.
  notes: >
    Deliberately curated with NO target_mechanisms block. The intended target
    was the uteroplacental vasculature, but randomised evidence shows no effect,
    and TreatmentEffectEnum offers only INHIBITS / ACTIVATES / MODULATES /
    BYPASSES / RESTORES - every one of which would assert an effect this drug
    does not have. Asserting a mechanism link and then contradicting it with
    REFUTE evidence would leave a false edge in the pathograph for any consumer
    reading edges without reading evidence. The refuting evidence is therefore
    held at treatment level. This is a schema observation worth surfacing: there
    is currently no way to record "this drug was tried against this node and did
    nothing", so rigorously tested negative therapies cannot be linked to the
    mechanism they failed to modify.

discussions:
- discussion_id: gap_fgr_no_in_utero_therapy
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >
    Can placental function be improved in utero once deficient spiral artery
    remodeling is established, or is the therapeutic window closed by the end of
    the first trimester?
  rationale: >
    This is the central unmet need of the entry and the reason its treatment
    section contains no disease-modifying therapy. The initiating lesion is laid
    down in early pregnancy, but FGR is not detected until the second or third
    trimester, so every candidate therapy is administered long after the
    remodeling failure is fixed. The STRIDER result is the strongest evidence
    available on this question: a drug with a coherent vasodilatory rationale,
    given to the right population, changed nothing - not pregnancy duration, not
    birthweight, not mortality. That null is consistent with the window having
    closed, but it does not distinguish this from the alternative explanation
    that sildenafil was simply the wrong agent.
  attaches_to:
  - pathophysiology#Deficient Uterine Spiral Artery Remodeling
  proposed_experiments:
  - experiment_id: exp_fgr_first_trimester_placental_therapy
    name: First-trimester-initiated placental therapy in a high-risk cohort
    description: >
      Test a candidate placental therapy started in the first trimester in women
      selected by prior severe early-onset FGR or by first-trimester uterine
      artery Doppler, with placental histopathology and exchange-capacity
      imaging as intermediate endpoints rather than birthweight alone. This
      addresses the timing confound directly: a null result at that point would
      be evidence about the agent, whereas a null result in the third trimester
      is uninterpretable between agent and timing.
  evidence:
  - reference: PMID:30169244
    reference_title: "Maternal sildenafil for severe fetal growth restriction (STRIDER): a multicentre, randomised, placebo-controlled, double-blind trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sildenafil did not prolong pregnancy or improve pregnancy outcomes in severe early-onset fetal growth restriction and therefore it should not be prescribed for this indication outside of research studies with explicit participants' consent."
    explanation: The negative randomised result that anchors the gap.

- discussion_id: gap_fgr_stem_villous_smc_causality
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >
    Does dedifferentiation of stem villous arterial smooth muscle cause the
    absent/reversed end-diastolic umbilical artery waveform, or are both
    downstream of a common placental vascular process?
  rationale: >
    The entry types this edge DIRECT because it is the best available
    mechanistic account of an otherwise unexplained imaging sign, but the source
    claims only a correlation, and the smooth muscle change is explicitly
    described as secondary. If the relationship is not causal, umbilical artery
    Doppler is a marker of placental disease severity rather than a readout of
    this specific lesion - which would not change how it is used clinically but
    would change what it licenses mechanistically. The same sentence is doing
    double duty in this entry: the word "Secondary" is also the only basis for
    the incoming INDIRECT_UNKNOWN_INTERMEDIATES edge from placental cell stress
    into this node, so if that ordering is wrong, both edges around this node
    are wrong together.
  attaches_to:
  - pathophysiology#Stem Villous Arterial Smooth Muscle Dedifferentiation
  evidence:
  - reference: PMID:29422210
    reference_title: Pathophysiology of placental-derived fetal growth restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Secondary changes involving dedifferentiation of smooth muscle cells surrounding the fetal arteries within placental stem villi correlate with absent or reversed end-diastolic umbilical artery blood flow, and with a reduction in birthweight."
    explanation: >
      The source's own wording - "secondary changes" and "correlate with" - is
      what makes this a gap rather than an established mechanism.

- discussion_id: gap_fgr_amino_acid_transport_not_universal
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >
    Why is placental system A amino acid transport reduced in growth-restricted
    pregnancies without preeclampsia but not in growth-restricted pregnancies
    with preeclampsia, when both share the same spiral artery lesion?
  rationale: >
    This is a genuine dissociation, not a null finding, and it constrains the
    model curated in this entry. If reduced amino acid transport were a simple
    downstream consequence of malperfusion, it should be present wherever
    malperfusion is - and it is most severe in FGR with preeclampsia, where the
    transport deficit is absent. The observation implies that the route from
    placental stress to fetal growth failure differs between the two
    presentations, which is why the entry does not treat FGR-with-preeclampsia
    as simply a more severe version of FGR alone.
  attaches_to:
  - pathophysiology#Impaired Placental Nutrient Transport
  evidence:
  - reference: PMID:18718657
    reference_title: "Placental system A amino acid transport is reduced in pregnancies with small for gestational age (SGA) infants but not in preeclampsia with SGA infants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We confirm the reduced uptake of amino acids in SGA pregnancies without preeclampsia but report that placental amino acid uptake of SGA infants with maternal preeclampsia is not reduced and is identical to uptake by normal and preeclamptic pregnancies with normal weight infants."
    explanation: Reports the dissociation in full, including that the preeclamptic SGA placentas were indistinguishable from normal.

- discussion_id: gap_fgr_definition_heterogeneity
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >
    How much of the inconsistency in the FGR literature is attributable to
    cohorts assembled on size thresholds (SGA) rather than on growth pathology
    (FGR)?
  rationale: >
    Any cohort defined by a size centile contains constitutionally small healthy
    fetuses and omits growth-restricted fetuses of normal size. Effect estimates
    from such cohorts are therefore biased toward the null by an unknown amount
    that varies with the threshold used and the reference population. The Delphi
    definition exists to fix this prospectively but cannot repair the
    retrospective literature, and the parallel problem in placental pathology is
    what the Amsterdam consensus addressed.
  attaches_to:
  - pathophysiology#Failure to Achieve Genetically Determined Growth Potential
  evidence:
  - reference: PMID:33972065
    reference_title: "Abnormal Fetal Growth: Small for Gestational Age, Fetal Growth Restriction, Large for Gestational Age: Definitions and Epidemiology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fetuses can be constitutionally small or large and thus healthy, whereas fetuses with seemingly normal size can be growth restricted or overgrown."
    explanation: States the bidirectional misclassification that drives the gap.
  - reference: PMID:27223167
    reference_title: "Sampling and Definitions of Placental Lesions: Amsterdam Placental Workshop Group Consensus Statement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The value of placental examination in investigations of adverse pregnancy outcomes may be compromised by sampling and definition differences between laboratories."
    explanation: Documents the same definitional-heterogeneity problem on the placental pathology side.

- discussion_id: fgr_microplastic_dose_translation_mismatch
  prompt: >-
    Does the nanoplastic-to-placental-ferroptosis mechanism shown in gestationally
    exposed mice operate at the plastic burdens actually measured in human
    placentas, or only at experimental doses far above them?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Placental Cell Stress Response
  - environmental#Placental micro- and nanoplastic accumulation
  rationale: >-
    The mechanism is not missing - it is worked out in unusual detail in rodents,
    down to a rescue arm. What is missing is the bridge to human exposure. Mice
    received 1-100 mg/kg/day of monodisperse 100 nm polystyrene by gavage for
    most of gestation; human placentas carry a mixed-polymer burden averaging
    roughly 127 micrograms per gram of tissue, acquired over years by ingestion
    and inhalation. The two differ in dose, in polymer identity, in particle size
    distribution, and in route. Until a human-relevant dose-response is
    established, a positive rodent result should not be read as evidence that
    environmental microplastic exposure causes FGR in people, and the negative
    case is equally open.
  proposed_experiments:
  - experiment_id: fgr_microplastic_burden_vs_ferroptosis_readouts
    name: Placental burden versus oxidative and ferroptotic markers in human FGR
    description: >-
      In prospectively collected placentas with recorded exposure history, pair
      quantitative polymer measurement (Py-GC-MS) with the ferroptosis and
      NAD-metabolism readouts the rodent work identifies, testing whether the
      proposed intermediates track burden within the human range rather than only
      above it.
    would_support:
    - pathophysiology#Placental Cell Stress Response
    supporting_outcome:
    - >-
      Placental NAD+ and nicotinamide fall, and lipid peroxidation markers rise,
      monotonically with measured polymer burden across the human range.
    refuting_outcome:
    - >-
      No relationship between polymer burden and the NAD/ferroptosis readouts
      across the human range, locating the rodent effect above environmental
      exposure.
  evidence:
  - reference: PMID:40796882
    reference_title: Gut microbiota contributes to polystyrene nanoplastics-induced fetal growth restriction by disturbing placental nicotinamide metabolism.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "pregnant mice were orally administered PS-NPs (approximately 100 nm in diameter) at different concentrations (1, 10, and 100 mg/kg/day) for 17.5 consecutive days"
    explanation: >-
      States the administered dose, particle size and route that the human
      comparison has to be made against.
  - reference: PMID:38366932
    reference_title: Quantitation and identification of microplastics accumulation in human placental specimens using pyrolysis gas chromatography mass spectrometry.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "averaging 126.8 ± 147.5 µg/g (mean±SD). Polyethylene was the most prevalent polymer, accounting for 54% of total NMPs"
    explanation: >-
      Gives the measured human placental burden and its dominant polymer, neither
      of which matches the rodent exposure.
differential_diagnoses:
- name: Constitutionally Small for Gestational Age
  description: >
    A healthy fetus that is small because its growth potential is small. This is
    the single most important differential, because it is the majority of
    fetuses below the 10th centile and because treating it as FGR leads to
    iatrogenic preterm delivery. Normal Doppler indices and growth that tracks
    along its own centile rather than crossing centiles are what distinguish it.
  distinguishing_features:
  - Normal umbilical and uterine artery Doppler indices
  - Normal amniotic fluid volume
  - Growth velocity maintained along a consistent centile rather than crossing centiles
  - No maternal vascular disease
  evidence:
  - reference: PMID:33972065
    reference_title: "Abnormal Fetal Growth: Small for Gestational Age, Fetal Growth Restriction, Large for Gestational Age: Definitions and Epidemiology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fetuses can be constitutionally small or large and thus healthy, whereas fetuses with seemingly normal size can be growth restricted or overgrown."
    explanation: States that constitutional smallness and growth restriction are distinct.
  - reference: PMID:26909664
    reference_title: "Consensus definition of fetal growth restriction: a Delphi procedure."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "two solitary parameters (AC or EFW < 3(rd) centile) and four contributory parameters (EFW or AC < 10(th) centile, AC or EFW crossing centiles by > two quartiles on growth charts and cerebroplacental ratio < 5(th) centile or UA-PI > 95(th) centile) were defined."
    explanation: >
      The contributory-parameter structure is precisely the discriminator: being
      under the 10th centile is not sufficient without centile crossing or a
      Doppler abnormality.

- name: Preeclampsia
  description: >
    Shares the initiating spiral artery lesion with FGR and frequently coexists
    with it, but is defined by the maternal syndrome of hypertension and
    end-organ involvement. It is a differential in the sense that growth
    restriction should prompt evaluation for preeclampsia, not that the two are
    mutually exclusive.
  disease_term:
    preferred_term: preeclampsia
    term:
      id: MONDO:0005081
      label: preeclampsia
  distinguishing_features:
  - Maternal hypertension with proteinuria or other end-organ dysfunction
  - More severe placental lesions when growth restriction and preeclampsia coexist
  - Placental system A amino acid transport unexpectedly preserved in the combination
  evidence:
  - reference: PMID:29422210
    reference_title: Pathophysiology of placental-derived fetal growth restriction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The changes are more severe in cases of growth restriction associated with preeclampsia compared to those with growth restriction alone, consistent with the greater degree of maternal vasculopathy reported in the former and more extensive macroscopic placental damage including infarcts, extensive fibrin deposition and microscopic villous developmental defects, atherosis of the spiral arteries, and noninfectious villitis."
    explanation: Contrasts the two presentations on placental lesion severity.

notes: >
  Ontology note. MONDO:0005030 fetal growth restriction is classified in MONDO
  under MONDO:0005917 placenta disorder, so anchoring a dismech Disease entry on
  it is consistent with MONDO's own placement. Issue #7837 previously listed
  fetal growth restriction among items believed blocked by a missing MONDO term;
  that was corrected in the 2026-08-13 comment on that issue, and this entry
  acts on the correction. MONDO's definition of the term is size-based ("A fetus
  that does not grow beyond the 10th percentile of conventionally accepted
  weight for gestational age"), which is the SGA framing that the field has
  explicitly moved away from - see the gap_fgr_definition_heterogeneity
  discussion. The entry follows the consensus potential-based definition rather
  than MONDO's definition text.

  Phenotype-term gap. The Stillbirth phenotype is deliberately unbound; see the
  note on that phenotype. This is the fourth entry in the KB to hit the same
  PhenotypeTerm enum-root gap.

  Schema gap. The sildenafil treatment is curated without a target_mechanisms
  link because TreatmentEffectEnum has no value for a tested-and-ineffective
  therapy; see that treatment's notes.

  Module conformance. Three nodes conform to deep_placentation_defect, the
  module created in response to the gap this note originally recorded: the
  spiral artery node, the malperfusion node and the placental stress node map
  onto its central effector and the two effector steps below it. Preeclampsia
  and Placental_Abruption conform to the same module at the spiral artery node,
  which is what this note anticipated - all three descend from the same
  deficient spiral artery remodeling lesion. Conformance to fibrotic_response
  was considered and rejected: the placental lesion here is hypoplasia and
  infarction with fibrin deposition, not myofibroblast-driven excessive ECM
  deposition, and fibrin deposition is not fibrosis.

  Provenance. No deep-research provider report was generated for this entry.
  References were identified by direct PubMed search and every one was fetched
  with `just fetch-reference` before any snippet was written.