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Fetal growth restriction (FGR)
Growth restriction is an estimated fetal weight or abdominal circumference below the 10th percentile; umbilical artery Doppler separates a small healthy fetus from a fetus whose placenta is failing, and decides when to deliver.
Why it matters in the exam
Questions present a woman with a fundal height smaller than expected or an ultrasound showing a small fetus, and ask for the next step and the timing of delivery. The answer rests on umbilical artery Doppler: normal diastolic flow allows waiting until 38–39 weeks, reduced flow brings delivery forward to 37 weeks, and absent or reversed diastolic flow requires a much earlier delivery. Before a delivery before 34 weeks steroids are given, and before 32 weeks magnesium as well.
Know the causes too: maternal (hypertension, preeclampsia, smoking, diabetes with vascular disease, malnutrition), placental (placental insufficiency, the common cause), and fetal (a chromosomal disorder, infection such as CMV, anomalies). Early, severe restriction before 32 weeks, especially with anomalies or polyhydramnios, suggests a fetal cause and justifies genetic testing. Bed rest and nutritional supplements do not improve growth; low-dose aspirin is used for prevention in women at high risk of preeclampsia, not as treatment. The newborn is at risk of hypoglycaemia, hypothermia and polycythaemia. It is also important to tell a constitutionally small fetus, which grows along a low but steady curve, from a fetus whose growth stalls between two scans — the second is far more worrying and needs close surveillance.
Key points
- FGR = EFW or abdominal circumference below the 10th percentile.
- Umbilical artery Doppler sets the surveillance and the timing of delivery.
- Normal → 38–39; 3rd percentile or reduced flow → 37; AEDV → 33–34; REDV → 30–32.
- Steroids before 34, magnesium before 32.
- Early FGR with anomalies → genetic and infection work-up.
Summary table
| Finding | Meaning | Surveillance | Timing of delivery |
|---|---|---|---|
| EFW at the 3rd–10th percentile, normal Doppler | Small fetus, probably without significant placental insufficiency | Doppler every 1–2 weeks | 38–39 weeks |
| EFW below the 3rd percentile | Severe restriction | Weekly Doppler | 37 weeks |
| Reduced umbilical artery diastolic flow | Placental insufficiency | Weekly Doppler | 37 weeks |
| Absent end-diastolic flow (AEDV) | Severe insufficiency | Surveillance twice a week or admission | 33–34 weeks |
| Reversed end-diastolic flow (REDV) | Immediate danger to the fetus | Admission and daily monitoring | 30–32 weeks |
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Sources
- SMFM Consult Series No. 52, 2020 — Diagnosis and management of fetal growth restriction
- ACOG Practice Bulletin No. 227, 2021 — Fetal Growth Restriction
- ISUOG Practice Guidelines, 2020 — Diagnosis and management of small-for-gestational-age fetus and fetal growth restriction
- Williams Obstetrics, 26th edition (2022) — Fetal-Growth Disorders
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.