Antenatal corticosteroid administration-to-delivery intervals and neonatal outcomes in late preterm labor: a historical cohort study

Abstract Background While antenatal corticosteroids (ACSs) are standard for early preterm birth, their benefit‒risk profile for the late preterm period is controversial, and the effect of the ACS-to-delivery interval on key neonatal morbidities is unclear. This study therefore examined the association between this interval and neonatal outcomes. Methods A historical cohort study enrolled 788 singleton pregnancies at 34+ 0 to 36+ 6 weeks of gestation. The non-ACS group comprised women who did not receive ACS. The ACS group was stratified into three subgroups according to the time between the first ACS dose and delivery: less than 2 days, between 2 and 7 days, and more than 7 days. The primary outcome was neonatal respiratory distress syndrome (NRDS), and neonatal hypoglycemia was a key secondary outcome. The associations between newborn outcomes and the intervals between ACS treatment and delivery were examined via multivariable logistic regression. Results Overall, ACS administration was not associated with reduced NRDS risk. However, this association significantly varied by the administration-to-delivery interval. Compared with the non-ACS group, a significantly lower NRDS risk was observed only in the 2–7 days subgroup [odds ratio (OR) = 0.468, 95% confidence interval (CI): 0.261–0.838, P = 0.011], but not in the < 2 days or > 7 days subgroups (both P > 0.05). In contrast, ACS use was associated with a significantly higher overall risk of neonatal hypoglycemia (OR = 2.594, 95% CI: 1.359–4.951, P = 0.004). This elevated risk was observed in both the < 2 days (OR = 2.922, 95% CI: 1.459–5.853, P = 0.002) and 2–7 days subgroups (OR = 2.641, 95% CI: 1.228–5.681, P = 0.013), but not when the interval exceeded 7 days. For other secondary outcomes, the need for mechanical ventilation was significantly reduced in the 2–7 days group (OR = 0.365, 95% CI: 0.152–0.873, P = 0.024). Conclusions In late preterm labor, ACS administration 2–7 days before delivery was associated with a lower risk of NRDS, whereas administration within 7 days was associated with a higher risk of neonatal hypoglycemia. These interval-dependent associations highlight the potential influence of timing on the benefit-risk profile of ACS and indicate the need for prospective validation.