Routine ultrasound at 32 vs 36 weeks’ gestation: prediction of small‐for‐gestational‐age neonates

OBJECTIVE: To evaluate and compare the performance of routine ultrasonographic estimated fetal weight (EFW) and fetal abdominal circumference (AC) at 31 + 0 to 33 + 6 and 35 + 0 to 36 + 6 weeks' gestation in the prediction of a small-for-gestational-age (SGA) neonate. METHODS: This was a prospective study of 21 989 singleton pregnancies undergoing routine ultrasound examination at 31 + 0 to 33 + 6 weeks' gestation and 45 847 undergoing routine ultrasound examination at 35 + 0 to 36 + 6 weeks' gestation. In each case, the estimated fetal weight (EFW) from measurements of fetal head circumference, AC and femur length was calculated using the Hadlock formula and expressed as a percentile according to The Fetal Medicine Foundation fetal and neonatal population weight charts. The same charts were used for defining a SGA neonate with birth weight  85% of SGA neonates with birth weight  85% of cases at 35 + 0 to 36 + 6 weeks' gestation necessitates use of EFW < 40th percentile. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.