Fetal Growth

Fetal growth restriction (FGR) complicates up to about 10% of pregnancies. The most common mechanism is placental disease: uteroplacental insufficiency limits the oxygen and nutrient supply reaching the fetus. A fetus affected by placental insufficiency may first adapt by redistributing cardiac output toward the brain, heart, and adrenal glands. As compensation becomes less effective, fetal movement, heart-rate reactivity, breathing activity, fluid volume, and eventually venous Doppler findings may become abnormal. That sequence explains why growth assessment and antenatal fetal health surveillance are linked. Ultrasound may identify a fetus that is small; surveillance helps determine whether that small fetus is coping with the placental environment. A small fetus is not automatically growth restricted. Some fetuses are constitutionally small and remain healthy. SOGC Guideline No. 442 defines late-onset FGR, beginning at 32+0 weeks, as either: - abdominal circumference (AC) or estimated fetal weight (EFW) below the 3rd percentile; or - at least two of the following: AC or EFW below the 10th percentile, crossing two quartiles on the growth chart, or abnormal Doppler findings such as umbilical artery pulsatility index above the...