Accuracy of clinical suspicion of growth restriction at term despite a normal growth ultrasound: A retrospective cohort study.

Abstract

Small for gestational age (SGA) is a major determinant of poor perinatal outcome. Detecting SGA at term using ultrasound is challenging and we often plan birth based on clinical assessment. To determine the incidence of SGA infants with birthweight <10th centile among women undergoing planned birth at term for suspected SGA despite a normal estimated fetal weight (EFW) on ultrasound at 35-37weeks. We performed a retrospective study including all women with a fetal growth ultrasound at ≥35weeks reporting an EFW≥10th centile (appropriate for gestational age, AGA) who subsequently had an induction of labour or caesarean birth at ≥37weeks due to ongoing clinical suspicion of SGA between 2012-2014. The primary outcome was the incidence of SGA newborns using customised centiles. There were 532 women who had a planned birth for clinical suspicion of SGA during the study period. Of these, 205 (38.5%) had an AGA fetus on ultrasound ≥35weeks but were subsequently delivered because of a persisting clinical suspicion of SGA on abdominal assessment. Sixty-eight percent (n=139/205) delivered an SGA infant. Furthermore, almost half of these SGA infants (47.5%) had a birthweight <3rd centile. Neonatal outcomes were worse for the SGA infants, with 15.1% (n=21/205) requiring special care nursery compared to 1.5% (n=1/205) of those AGA at birth. A reassuring ultrasound with EFW ≥10th centile in the late third trimester should not override clinical concerns of impaired fetal growth at term.