Antenatal Corticosteroid Administration in Late Preterm Singleton Pregnancies: A Propensity Score-Weighted Analysis of Neonatal Outcomes

Objective: To evaluate the association between antenatal corticosteroid exposure in late preterm singleton pregnancies (34+0–36+6 weeks) and neonatal outcomes using propensity score-weighted analysis. Study Design: Retrospective single-center cohort of 1,012 singleton late preterm deliveries (2017–2022), excluding 75 pregnancies with antenatal corticosteroid exposure before 34 weeks. Late-preterm exposure occurred in 126 pregnancies; 886 were unexposed. Stabilized inverse probability of treatment weighting, trimmed at the 1st and 99th percentiles, used prespecified maternal, obstetric, delivery, and fetal covariates. The primary outcome was documented initial respiratory support at birth. Results: Initial respiratory support occurred in 34.1% (43/126) of exposed neonates versus 25.2% (223/886) of unexposed neonates; weighted analysis did not show lower odds with exposure (odds ratio, 1.40; 95% confidence interval, 0.90–2.18; P = .130). Among exposed pregnancies, 85.7% received a single documented dose and 55.6% delivered within 24 hours. Neonatal hypoglycemia occurred in 3.2% versus 1.1% (odds ratio, 2.14; 95% confidence interval, 0.63–7.28; P = .224). No secondary outcomes remained significant after false discovery rate correction. Conclusion: In this real-world cohort with predominantly single-dose exposure and short ACS-to-delivery intervals, late preterm antenatal corticosteroids were not associated with reduced initial respiratory support. These hypothesis-generating findings support selective rather than routine administration with individualized risk assessment and neonatal glucose monitoring.