Survival without severe neonatal morbidity after antenatal betamethasone dose reduction: a post hoc analysis of a randomized non-inferiority trial

BACKGROUND: Antenatal betamethasone is recommended before preterm delivery to accelerate fetal lung maturation. However, its optimal dose remains unknown. A 50% dose reduction was proposed to decrease the potential dose-related long-term neurodevelopmental side effects, including psychological development, sleep, and emotional disorders. Because noninferiority of the half dose in terms of the need for exogenous surfactant was not shown in the primary analysis, its impact on survival without major neonatal morbidity needs to be investigated. OBJECTIVE: This study aimed to investigate the impact of antenatal betamethasone dose reduction on survival of very preterm infants without severe neonatal morbidity, a factor known to have a strong correlation with long-term outcomes. STUDY DESIGN: We performed a post hoc secondary analysis of a randomized, multicenter, double-blind, placebo-controlled, noninferiority trial, testing half (11.4 mg once; n=1620) vs full (11.4 mg twice, 24 hours apart; n=1624) antenatal betamethasone doses in women at risk of preterm delivery. To measure survival without severe neonatal morbidity at hospital discharge among neonates born before 32 weeks of gestation, we used the definition of the French national prospective study on preterm children, EPIPAGE 2, comprising 1 of the following morbidities: grade 3 to 4 intraventricular hemorrhage, cystic periventricular leukomalacia, necrotizing enterocolitis stage ≥2, retinopathy of prematurity requiring anti-vascular endothelial growth factor therapy or laser, and moderate-to-severe bronchopulmonary dysplasia. RESULTS: After exclusion of women who withdrew consent or had pregnancy termination and of participants lost to follow-up (8 in the half-dose and 10 in the full-dose group), the rate of survival without severe neonatal morbidity among neonates born before 32 weeks of gestation was 300 of 451 (66.5%) and 304 of 462 (65.8%) in the half-dose and full-dose group, respectively (risk difference, +0.7%; 95% confidence interval, -5.6 to +7.1). There were no significant between-group differences in the cumulative number of neonatal morbidities. Results were similar when using 2 other internationally recognized definitions of severe neonatal morbidity and when considering the overall population recruited in the trial. CONCLUSION: In the BETADOSE trial, severe morbidity at discharge of newborns delivered before 32 weeks of gestation was found to be similar among those exposed to 11.4-mg and 22.8-mg antenatal betamethasone. Additional studies are needed to confirm these findings.