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

Objective To 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. Methods This 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 Trial Results The 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. Conclusion The 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study did not receive any funding. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Mass General Brigham IRB waived ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data used in this study are publicly available via the NICHD's Data and Specimen Hub ().