FGR is defined by size AND function (Delphi consensus): an EFW or AC below the 3rd centile, or below the 10th with abnormal Doppler; the umbilical artery, MCA, cerebroplacental ratio, uterine arteries and ductus venosus stage it — early versus late FGR behave differently.
Orient first
- Early FGR (< 32 weeks) is placental with progressive Doppler deterioration; late FGR shows subtle cerebral redistribution with near-normal umbilical Doppler.
- Umbilical artery absent or reversed end-diastolic flow and ductus venosus abnormalities drive delivery timing.
- Use the calculators (Growth, UA-PI, MCA, CPR) against the standard your unit uses.
Acquire the study
- Transabdominal ultrasound: HC, AC, FL (and BPD) to standard; EFW (Hadlock); spectral Doppler of the umbilical artery (free loop), MCA (near the circle of Willis, angle ≈ 0°), uterine arteries and ductus venosus; amniotic fluid.
The manoeuvre
- Biometry in mm in the standard planes; EFW and AC centiles against the named standard.
- Umbilical artery PI from a free loop, fetus quiet; end-diastolic flow present, absent or reversed.
- MCA PI with the angle of insonation near 0°; cerebroplacental ratio (MCA PI / UA PI).
- Ductus venosus a-wave (absent or reversed = severe).
- Uterine artery mean PI; amniotic fluid deepest pocket in cm.
- Interval growth: repeat biometry no sooner than 2 weeks.
What confirms it
- Consensus criteria met — size with or without abnormal Doppler — with early or late type stated.
What licenses you to exclude it
- EFW and AC above the 10th centile with normal Doppler and normal growth velocity exclude FGR on this scan.
The classic misread
- Diagnosing FGR on a single borderline measurement with wrong dating — check the CRL-dated age.