Diagnosis of fetal growth restriction in a cohort of small-for-gestational-age neonates at term: neonatal and maternal outcomes

Abstract

Small-for-gestational-age neonates (birthweight of <10th percentile for gestational age) are significantly more likely to have multiple adverse outcomes than appropriate-for-gestational-age neonates (birthweight of 10th-90th percentile). Most small-for-gestational-age neonates are undetected during pregnancy (ie, not diagnosed as fetal growth restriction), but the sequela of being undetected remains uncertain. The primary objective of this study was to compare the composite neonatal adverse outcomes among singleton pregnancies that were at least 37 weeks and delivered small-for-gestational-age neonates, which were diagnosed as either fetal growth restriction during pregnancy (detected small for gestational age) or not (undetected small for gestational age). This was a secondary analysis of a retrospective cohort, the Consortium for Safe Labor. Singleton births at 37.0 to 41.6 weeks of gestation without congenital anomalies born small for gestational age were included in the analysis. The primary outcome was the rate of composite neonatal adverse outcome, defined as any of the following: Apgar score of <5 at 5 minutes, cardiopulmonary resuscitation at birth, respiratory distress syndrome, continuous positive airway pressure, mechanical ventilation, neonatal seizures, hypoxic-ischemic encephalopathy or diagnosis of asphyxia, intraventricular hemorrhage, necrotizing enterocolitis, neonatal sepsis, or fetal or neonatal death. The secondary outcome was the rate of composite maternal adverse outcome, which included any of the following: postpartum hemorrhage, peripartum infection, thromboembolism, hysterectomy, uterine rupture, eclampsia, intensive care unit admission, or maternal death. Small for gestational age with a prenatal diagnosis of fetal growth restriction (detected small for gestational age) was compared with small for gestational age without a prenatal diagnosis of fetal growth restriction (undetected small for gestational age). Multivariate logistic regression models were used to compare groups. A P value of <.05 was considered statistically significant. Gestational age-specific risks of composite neonatal adverse outcome and perinatal death were computed for each week of gestation among ongoing pregnancies. Of the 228,438 deliveries in the Consortium for Safe Labor, 18,607 (8.1%) met the inclusion criteria. Among these deliveries, 17,689 (95.0%) were undetected small for gestational age, and 918 (5.0%) were detected small for gestational age. The overall rate of composite neonatal adverse outcome was 3.0%. Moreover, the rate of composite neonatal adverse outcome was similar between undetected small for gestational age and detected small for gestational age (3.0% vs 3.9%, respectively; adjusted odds ratio, 1.33; 95% confidence interval, 0.88-2.00). Some components of the composite-respiratory distress syndrome, mechanical ventilation, and necrotizing enterocolitis-were significantly higher among undetected small for gestational age than among detected small for gestational age. The overall rate of composite maternal adverse outcome was 6.2%. The rate of composite maternal adverse outcome between undetected small for gestational age and detected small for gestational age (6.2% vs 5.1%, respectively; adjusted odds ratio, 0.84; 95% confidence interval, 0.60-1.18) was similar. In gestational age-specific comparisons of composite neonatal adverse outcome, no difference was found between the undetected small-for-gestational-age group and the detected small-for-gestational-age group except for in pregnancies >41 weeks. In pregnancies at 41.0 to 41.6 weeks, the rate of composite neonatal adverse outcome was significantly greater in detected small for gestational age than in undetected small for gestational age (10.0% vs 2.5%, respectively; P=.035). Antenatal detection of small for gestational age was not associated with improved composite neonatal adverse outcomes, although some components of morbidity improved with detection. Maternal outcomes did not differ between detected small for gestational age and undetected small for gestational age.