Booster course of antenatal corticosteroids after preterm prelabor rupture of membranes: a double-blind randomized trial.

BACKGROUND: Preterm prelabor rupture of membranes is a leading cause of preterm birth and is responsible for 18% to 20% of perinatal deaths in the United States. An initial course of antenatal corticosteroids has been shown to reduce morbidity and mortality in patients with preterm prelabor rupture of membranes. For patients who remain undelivered for 7 days or more after the initial course of antenatal corticosteroids, it is uncertain whether a booster course of antenatal corticosteroids reduces neonatal morbidity or increases the infection risk. The American College of Obstetricians and Gynecologists has concluded that the current evidence is insufficient to make a recommendation.

OBJECTIVE: This study aimed to evaluate if a single booster course of antenatal corticosteroids improves neonatal outcomes after preterm prelabor rupture of membranes.

STUDY DESIGN: We conducted a multicenter, placebo-controlled randomized clinical trial. The inclusion criteria were preterm prelabor rupture of membranes, gestational age of 24.0 to 32.9 weeks, singleton, initial antenatal corticosteroid course administered at least 7 days before randomization, and planned expectant management. Consenting patients were randomized in gestational age blocks to either receive booster antenatal corticosteroids (12 mg betamethasone every 24 hours for 2 days) or a saline placebo. The primary outcome was composite neonatal morbidity or death. A sample size of 194 patients was calculated to yield 80% power at P<.05 to detect a reduction in primary outcome from 60% in placebo group to 40% in antenatal corticosteroids group.

RESULTS: From April 2016 through August 2022, 194 patients consented and were randomized (47% of 411 eligible patients). Intent-to-treat analysis was performed on 192 patients (2 placebo patients left hospital, outcomes unknown). The groups had similar baseline characteristics. The primary outcome occurred in 64% of patients who received booster antenatal corticosteroids vs in 66% of patients who received the placebo (odds ratio, 0.82; 95% confidence interval, 0.43-1.57; gestational age-stratified Cochran-Mantel-Haenszel test). Individual components of the primary outcome and secondary neonatal and maternal outcomes were not significantly different between the antenatal corticosteroids and placebo groups. Specifically, chorioamnionitis (22% vs 20%), postpartum endometritis (1% vs 2%), wound infections (2% vs 0%), and proven neonatal sepsis (5% vs 3%) were not different between the groups.

CONCLUSION: A booster course of antenatal corticosteroids at least 7 days after the first antenatal corticosteroids course in patients with preterm prelabor rupture of membranes did not improve neonatal morbidity or any other outcome in this adequately-powered, double-blind randomized clinical trial. Booster antenatal corticosteroids did not increase maternal or neonatal infection.