Prenatal identification of small-for-gestational age and risk of neonatal morbidity and stillbirth

Abstract

Objective: To assess whether prenatal identification of small-for-gestational age (SGA) was associated with lower rates of the primary composite outcome of stillbirth, death in the delivery room or neonatal complications, and secondary outcomes of the composite outcome according to gestational age at delivery, stillbirth and low 5-min Apgar score. Methods: This historical cohort study included women who had a singleton delivery (≥ 32 weeks) between 1994 and 2011 at one of 247 French maternity units. We excluded pregnancies terminated medically, infants with malformations or with missing data on estimated fetal weight or birth weight, and women with missing delivery data. Among the 24 946 infants born SGA (' 5th percentile), we compared those who had been identified as such prenatally (n = 5093; 20%), with those who had not (n = 19 853; 80%). The main outcome was a composite variable defined as stillbirth or death in the delivery room, or transfer to a neonatal department either immediately or during the neonatal stay in the obstetrics ward. Secondary outcomes were the composite outcome according to gestational age at delivery (32 to ' 35 weeks; 35 to ' 37 weeks, 37 to ' 40 weeks, or ≥ 40 weeks), stillbirth and low 5-min Apgar score (≤ 4 and ' 7). Results: The mean ± SD birth weight was 2449.1 ± 368.3 g. The rate of the main composite outcome was higher in the group identified prenatally as SGA compared with non-identified SGA fetuses (39.5% vs 13.5%; adjusted relative risk (aRR), 1.29; 95% CI, 1.21–1.38). This association was not observed in the subgroups delivered before 37 weeks. The stillbirth rate was lower in fetuses with prenatal suspicion of SGA (aRR, 0.47; 95% CI, 0.27–0.79), while the 5-min Apgar score did not differ between the two groups. The a-posteriori study power with α = 0.05 was 99%. Conclusion: Prenatal identification of SGA was not associated with lower fetal or neonatal morbidity overall, although it was associated with a lower rate of stillbirth. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.