Abstract
BACKGROUND: Antenatal corticosteroids, specifically betamethasone, administered to patients at risk for late preterm delivery have been associated with reduced rates of neonatal respiratory complications. However, whether these risks vary by delivery indication among betamethasone-exposed, late-preterm infants is not known. OBJECTIVE: This study aimed to evaluate if spontaneous preterm labor or preterm prelabor rupture of membranes, compared with indicated late preterm delivery, is associated with better neonatal respiratory outcomes after accounting for betamethasone administration in the late preterm period. STUDY DESIGN: This was a secondary analysis of the Antenatal Late Preterm Steroids trial, a multicenter, placebo-controlled trial in which patients with singleton pregnancies at risk for delivery at 34 0/7 to 36 5/7 weeks of gestation were randomized to a single course of antenatal corticosteroids (betamethasone) or placebo. Patients were eligible if they had spontaneous preterm labor, preterm prelabor rupture of membranes, or if they were undergoing indicated late preterm delivery. The primary outcome was a composite of need for respiratory support, stillbirth, or neonatal death within 72 hours after delivery. Secondary outcomes included individual neonatal morbidities. Bivariate analyses were performed, and multivariable logistic regression models were used to control for potential confounders. Using the indicated preterm delivery group as the reference group, adjusted odds ratios and 95% confidence intervals were calculated for the outcomes by delivery indication. Subgroup analyses separately examined the treatment and placebo groups to determine the odds of the primary outcome by delivery indication. RESULTS: Of 2827 participants at high risk for late preterm delivery, 1427 (50.5%) received betamethasone. There were 790 (27.9%) infants born after preterm labor, 620 (21.9%) born after preterm prelabor rupture of membranes, and 1417 (50.1%) born after indicated preterm delivery. Compared with indicated preterm delivery, the odds of the primary outcome were lower among those born after preterm labor (7.3% vs 16.4%; adjusted odds ratio, 0.57; 95% confidence interval, 0.40-0.82) and among those born after preterm prelabor rupture of membranes (12.4% vs 16.4%; adjusted odds ratio, 0.49; 95% confidence interval, 0.35-0.69). Preterm labor had lower odds of all neonatal complications except feeding problems, and preterm prelabor rupture of membranes had lower odds of all neonatal complications except newborn intensive care unit admission for ≥3 days when compared with indicated preterm delivery. For the placebo group, the odds of the primary outcome were lower for the preterm labor group (8.2% vs 18.5%; adjusted odds ratio, 0.55; 95% confidence interval, 0.34-0.91) and the preterm prelabor rupture of membranes group (13.2% vs 18.5%; adjusted odds ratio, 0.46; 95% confidence interval, 0.29-0.73) than for the indicated preterm delivery group. For those exposed to betamethasone, the odds of the primary outcome remained lower for the preterm labor group (6.5% vs 14.3%; adjusted odds ratio, 0.58; 95% confidence interval, 0.34-0.99) and the preterm prelabor rupture of membranes group (11.7% vs 14.3%, adjusted odds ratio, 0.56; 95% confidence interval, 0.34-0.91) than for the indicated preterm delivery group. CONCLUSION: Compared with indicated preterm delivery, preterm labor and preterm prelabor rupture of membranes were associated with reduced odds of neonatal respiratory complications irrespective of betamethasone exposure in the late preterm period.