Fetal Growth Restriction Criteria Interpreter

The Delphi consensus definition of early and late fetal growth restriction, applied exactly as published. The two branches use different logic — early needs a size criterion AND a Doppler, late needs two of three — and that asymmetry is the point.

Last updated 8 Oct 2026

Delphi consensus FGR criteria

Early and late branches

Any congenital anomaly identified?Both halves of the consensus definition are explicitly written ‘in absence of congenital anomalies’. A small fetus with an anomaly is small for a reason the definition does not describe, and the criteria were not derived in that population. This field is first because it is an exclusion, not a modifier.

Gestational age (completed weeks)The 32-week line divides the two branches, and it is a hard boundary rather than a gradient: before 32 weeks 0 days the early criteria apply and the uterine artery pulsatility index counts; from 32 weeks 0 days the late criteria apply, the uterine artery drops out entirely, and centile crossing and the cerebroplacental ratio come in. Date the pregnancy from the earliest accurate scan, not from this one.

Abdominal circumference or estimated fetal weight centileEither measurement qualifies — the definition reads AC/EFW throughout, so an abdominal circumference below the threshold counts even when the estimated weight is not. Record which standard the centile came from: the same fetus crosses the 10th centile or not depending on it. The z-score and centile page converts a weight and your standard’s reference mean and SD into a centile.

Umbilical artery DopplerAbsent and reversed end-diastolic flow are CATEGORICAL findings and are reported as such rather than as an index value or a centile. Before 32 weeks absent end-diastolic flow is a solitary criterion in its own right. From 32 weeks it is not named in the definition at all, which does not make it normal — see what this page says when you select it there.

Uterine artery pulsatility indexCounts in the EARLY branch only. From 32 weeks 0 days the consensus definition does not use the uterine artery at all, and this field then has no effect on the answer — which is itself worth knowing, because a raised uterine artery index at 34 weeks does not contribute to the definition however abnormal it looks.

Cerebroplacental ratioCounts in the LATE branch only, and it shares its criterion with the umbilical artery pulsatility index: the definition reads ‘CPR below the 5th centile OR UA-PI above the 95th centile’ as ONE of the three, so a low ratio and a raised umbilical index together still count once. The Doppler ratio calculator computes the ratio, and gets the direction the right way round.

AC or EFW crossing centiles by more than two quartilesLATE branch only, and it needs at least two measurements separated in time — a single scan cannot see it. The consensus definition specifies NON-CUSTOMISED growth centiles for this criterion specifically, which is unusual and deliberate: customisation adjusts for the mother’s own characteristics and would partly absorb the change the criterion is trying to detect.

Late fetal growth restriction: the contributory criteria are metExample

34 weeks, no anomaly; AC/EFW between the 3rd and 10th centile; umbilical artery PI above the 95th centile; uterine artery, CPR and centile crossing all normal

The consensus definition

EARLY (before 32 weeks, no congenital anomaly): AC/EFW below the 3rd centile OR absent umbilical end-diastolic flow — OR — AC/EFW below the 10th centile COMBINED WITH uterine artery PI above the 95th centile and/or umbilical artery PI above the 95th centile
LATE (32 weeks and over, no congenital anomaly): AC/EFW below the 3rd centile — OR at least TWO OF THREE: AC/EFW below the 10th centile; AC/EFW crossing centiles by more than two quartiles; CPR below the 5th centile or umbilical artery PI above the 95th centile

the two branches use different logic: and this is the thing to get right. Early is a size criterion AND a Doppler criterion. Late is two out of three. Applying the late branch’s arithmetic before 32 weeks would let raised Dopplers plus centile crossing meet the definition with no size criterion at all, which the early branch does not allow
how it was agreed: a four-round Delphi procedure: 106 experts invited, 56 entering the first round, 45 completing all four. It is a consensus definition for research and reporting rather than a prediction rule, so it has no sensitivity or specificity of its own
the third late criterion is ONE criterion: a cerebroplacental ratio below the 5th centile OR an umbilical artery index above the 95th. Both together still count once; counting them separately turns a one-criterion fetus into a two-criterion one and is the commonest way this definition is over-applied
small is not growth restricted: the whole reason this definition exists. A small fetus below the 10th centile with normal Dopplers and normal growth velocity does not meet it; a fetus above the 10th centile that has crossed two quartiles with a low cerebroplacental ratio does

Worked example

34 weeks, no anomaly; AC/EFW between the 3rd and 10th centile; umbilical artery PI above the 95th centile; uterine artery, CPR and centile crossing all normal
34 weeks is 32 or more, so the LATE branch applies and the uterine artery drops out of the definition entirely
The solitary criterion (below the 3rd centile) is not met
Counting the three contributory criteria: AC/EFW below the 10th centile — yes; crossing more than two quartiles — no; CPR below the 5th centile or umbilical PI above the 95th — yes
Two of three, so the definition is met
Change only the gestational age to 31 weeks and the EARLY branch applies, needing a size criterion COMBINED WITH a raised Doppler — still satisfied here by the umbilical artery. Same answer, different logic. Set the umbilical artery back to normal at 31 weeks and the definition is no longer met
Back at 34 weeks, set the CPR below the 5th centile as well as the raised umbilical PI. The answer does not change, because those two are the SAME third criterion and cannot be counted twice

The Delphi consensus definition, both branches

Both branches apply only absent congenital anomalies. The connectives are the content: ‘combined with’ in the early branch is a conjunction, ‘at least two of three’ in the late branch is not. Agreed by 45 experts over four Delphi rounds.
Branch	Solitary criteria	Contributory criteria
Early, before 32 weeks	AC/EFW below the 3rd centile, OR absent umbilical artery end-diastolic flow	AC/EFW below the 10th centile COMBINED WITH uterine artery PI above the 95th centile and/or umbilical artery PI above the 95th centile
Late, 32 weeks and over	AC/EFW below the 3rd centile	At least two of three: AC/EFW below the 10th centile; AC/EFW crossing centiles by more than two quartiles on non-customised growth centiles; CPR below the 5th centile or umbilical artery PI above the 95th centile

Where the two branches give different answers to the same findings

Each row flips its answer at the 32-week line, and every one is a probe this page is tested against. The third is the one worth remembering: after 32 weeks a fetus that is not small at all can meet the definition on growth velocity and a Doppler ratio — the late-onset phenotype a centile threshold misses.
Findings	Before 32 weeks	From 32 weeks
AC/EFW 3rd to 10th centile, all Dopplers normal, no serial measurements	Not met — the early branch needs a Doppler too	Not met — one of three
AC/EFW 3rd to 10th centile, uterine artery PI above the 95th centile only	MET, contributory combination	Not met — the uterine artery is not a late criterion
AC/EFW at or above the 10th centile, crossing two quartiles, CPR below the 5th centile	Not met — neither is an early criterion	MET, two of three, with no size criterion at all
Absent umbilical end-diastolic flow, AC/EFW above the 10th centile	MET, solitary criterion	Not met by the definition — flagged separately on this page

Why a consensus definition, and why the two halves are not symmetrical

Small for gestational age and growth restricted are different things, and conflating them is the problem this definition was written to solve. A constitutionally small fetus with normal Dopplers and normal growth velocity is below the 10th centile and healthy; a fetus that has fallen from the 60th centile to the 25th with a low cerebroplacental ratio is above every centile threshold and is not. Before 2016 the literature used a dozen incompatible definitions, which made trials uncombinable. Gordijn and colleagues ran a four-round Delphi procedure — 106 experts invited, 56 in the first round, 45 completing all four — and produced these criteria.

The two branches are deliberately asymmetrical, and that is the part most often got wrong. Early-onset restriction is a placental disease with a recognisable Doppler signature, so the early branch pairs a size criterion with a Doppler one: below the 10th centile combined with a raised uterine or umbilical pulsatility index. Late-onset disease is different — the umbilical artery is often normal, the fetus may not be small, and what changes is growth velocity and cerebral redistribution — so the late branch takes two out of three, brings in centile crossing and the cerebroplacental ratio, and drops the uterine artery entirely. An interpreter applying one branch’s logic at the other gestation would be wrong in both directions at once.

Two limits are worth stating. This is a consensus definition rather than a prediction rule: it has no sensitivity or specificity of its own, because it defines the condition rather than predicting an outcome, and the performance figures in the literature belong to its individual components. And every centile in it depends on the standard it was read against. Fetal size standards are not interchangeable: Hadlock, INTERGROWTH-21st, the WHO charts and customised standards such as GROW were built on different populations, and a fetus can cross a centile threshold purely by changing standard. In 117,027 UK singleton pregnancies 7.2% were small for gestational age by GROW and 2.4% by INTERGROWTH-21st, two-thirds of the GROW cases being missed (Hugh et al., Ultrasound Obstet Gynecol 2025; the authors work for the institute that developed GROW). Record which standard a centile came from. The definition specifies non-customised centiles for the crossing criterion only and leaves the standard open elsewhere, so two units applying the same criteria faithfully can reach different answers on the same fetus. This page computes a number, or applies published criteria, and names the body that publishes them. It renders no clinical decision: nothing here says whether this fetus is growth restricted, whether a scan should be repeated, whether labour should be induced or when a pregnancy should be delivered. An obstetric measurement is read alongside the whole clinical picture — history, serial trend, the other biometry — and never instead of it. It supports a clinician’s judgement rather than replacing it.

Frequently asked questions

What is the difference between small for gestational age and fetal growth restriction?

Small for gestational age is a size threshold, conventionally below the 10th centile. Growth restriction is a failure to achieve growth potential, and the Delphi definition requires either a centile below the 3rd or a combination of findings. A constitutionally small fetus is the first without being the second; a fetus that has crossed centiles with abnormal Dopplers can be the second without the first.

Why does the definition split at 32 weeks?

Because early and late onset behave differently. Before 32 weeks it is typically placental with a clear umbilical and uterine Doppler signature; after it the umbilical artery is often normal and what changes is growth velocity and cerebral redistribution. So the uterine artery counts only before 32 weeks, and centile crossing and the cerebroplacental ratio only after.

Do a low cerebroplacental ratio and a raised umbilical index count as two criteria?

No. In the late branch they are the same third criterion, written as ‘CPR below the 5th centile or UA-PI above the 95th centile’. Both together still count once. Counting them separately is the commonest way the definition gets applied too generously.

What about absent end-diastolic flow after 32 weeks?

It is a solitary criterion before 32 weeks and is not named in the late branch at all. This page flags it separately rather than reporting the criteria as simply not met, because that is a limit of the definition and not a reassurance.

Does the growth standard change whether the criteria are met?

Yes, substantially. In 117,027 UK singleton pregnancies, 7.2% were small for gestational age by a customised standard and 2.4% by INTERGROWTH-21st, with two-thirds of the customised-standard cases missed. The consensus definition specifies non-customised centiles for the crossing criterion only and leaves the standard open elsewhere, so record which one was used.

Related calculators

References

Gordijn SJ, Beune IM, Thilaganathan B, et al. Consensus definition of fetal growth restriction: a Delphi procedure. Ultrasound Obstet Gynecol. 2016;48(3):333-9.
Hugh O, Butler E, Ellson H, Mytton J, Gardosi J. Small-for-gestational age according to INTERGROWTH-21st fetal weight standard misses most pregnancies at risk of stillbirth identified by GROW. Ultrasound Obstet Gynecol. 2025.
Seravalli V, Hecher K, Baschat AA. A critical review of placental function evaluation near term using Doppler ratios. Am J Obstet Gynecol. 2025. doi:10.1016/j.ajog.2025.11.032
Lappen JR, Myers SA. The systematic error in the estimation of fetal weight and the underestimation of fetal growth restriction. Am J Obstet Gynecol. 2017;216(5):477-83.

Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/