A comparison of 2 doses of antenatal dexamethasone for the prevention of respiratory distress syndrome: an open-label, noninferiority, pragmatic randomized trial

Background: Antenatal corticosteroids have been used for the prevention of respiratory complications, intraventricular hemorrhage, necrotizing enterocolitis, and other adverse neonatal outcomes for over 50 years, with limited evidence about their optimal doses. Higher steroid doses or frequencies of antenatal corticosteroids in preterm newborns pose adverse effects such as prolonged adrenal suppression, negative effects on fetal programming and metabolism, and increased risks of neurodevelopmental and neuropsychological impairments. Conversely, lower doses of antenatal corticosteroids may be an effective alternative to induce fetal lung maturation with less risk to the fetus. Late preterm births represent the largest population of all preterm neonates, with a respiratory distress syndrome risk of 8.83%. Therefore, determining the optimal antenatal corticosteroid dosage is of particular importance for this population. Objective: This study aimed to compare the efficacy of 5-mg and 6-mg dexamethasone in preventing neonatal respiratory distress syndrome in women with preterm births at 32(0) to 36(6) weeks of gestation. Study Design: This was an open-label, randomized, controlled, noninferiority trial. Singleton pregnant women (n=370) at 32(0) to 36(6) weeks of gestation with spontaneous preterm labor or preterm premature rupture of membranes were enrolled. They were randomly assigned (1:1) to a 5-mg or 6-mg dexamethasone group. Dexamethasone was administered intramuscularly every 12 hours for 4 doses or until delivery. The primary outcome was the reduction in neonatal respiratory distress syndrome cases, whereas the secondary outcomes were any adverse maternal or neonatal events. Results: Between December 2020 and April 2022, 370 eligible women, anticipating deliveries within the gestational range of 32 0/7 to 36 6/7 weeks, willingly participated in the study. They were evenly split, with 185 women assigned to the 5-mg group and 185 to the 6-mg group. The study revealed that the demographic profiles of the participants in the 2 groups were remarkably similar, with no statistically significant disparities (P>.05). It is noteworthy that most of these women gave birth after 34 weeks of gestation. Despite a substantial proportion not completing the full course of steroid treatment, the 5-mg dose exhibited noninferiority compared with the 6-mg dose of dexamethasone, as indicated by a modest proportional difference of 0.5% (95% confidence interval, -2.8 to 43.9). Neonatal respiratory distress syndrome occurred in a relatively low percentage of newborns in both groups, affecting 2.2% in the 5-mg group and 1.6% in the 6-mg group. Notably, the risk difference of 0.6% fell comfortably within the predefined noninferiority threshold of 10%. Conclusion: Our study suggests that a 5-mg dexamethasone dose is noninferior to a standard 6-mg dose in preventing neonatal respiratory distress syndrome in preterm births.