Neonatal Respiratory Morbidity among Late Preterm Births by Planned Mode of Delivery and Gestational Age

Abstract

AbstractObjectiveTo estimate the effect of late preterm antenatal steroids on the absolute risk of respiratory morbidity among subgroups of patients based on the planned mode of delivery and gestational age at presentation.MethodsThis was a secondary analysis of the Antenatal Late Preterm Steroid (ALPS) Trial, a multicenter trial originally conducted within the NICHD’s MFMU network of individuals with singleton gestations and without pre-existing diabetes who were at high risk for late preterm delivery (34-36 weeks of gestation). We fit binomial regression models to estimate the absolute risk of respiratory morbidity, with and without steroid administration, by gestational age and planned mode of delivery at the time of presentation. We assumed a homogenous effect of steroids on the log-odds scale, as was reported in the ALPS trial. The primary outcome was neonatal respiratory morbidity, as defined in the ALPS TrialResultsThe analysis included 2,825 patients at risk for late preterm birth. The risk of respiratory morbidity varied significantly by planned mode of delivery (adjusted risk ratio (aRR) 1.90 (95% confidence interval (CI) 1.55, 2.33) for cesarean compared to vaginal delivery) and day of gestation at presentation (aRR 0.92 (95% CI 0.90, 0.94)). For those planning a cesarean delivery and presenting in the 34th week of gestation, the risk of neonatal respiratory morbidity was 39.4% (95% CI 30.8, 47.9%) without steroids and 32.0% (95% CI 24.6, 39.4%) with steroids. In contrast, for patients presenting in the 36th week and planning a vaginal delivery, the risk of neonatal respiratory morbidity was 6.9% (95% CI 5.6, 8.6%) without steroids and 5.6% (95% 4.2, 7.0%) with steroids.ConclusionThe absolute risk of neonatal respiratory morbidity among patients at risk for late preterm delivery varies considerably by gestational age at presentation and planned mode of delivery. As only communicating the relative risk reduction of antenatal steroids for respiratory morbidity may lead to an inaccurate perception of benefit, individualized estimates of absolute risk expected with and without treatment may inform shared decision-making.