Risk of complications in the late vs early days of the 42nd week of pregnancy: A nationwide cohort study

Introduction: Uncertainty remains about the most appropriate timing of induction of labor in late-term pregnancies. To address this issue, this study aimed to compare the risk of neonatal morbidity and pregnancy- and birth-related complications between gestational age (GA) 41⁺⁴–42⁺⁰ and GA 41⁺⁰–41⁺³ weeks. Material and methods: This nationwide registry-based cohort study included singleton births without major congenital malformations, with registered GA, and with intended vaginal delivery at GA 41⁺⁰– 42⁺⁰ weeks between 2009 and 2018 in Denmark. Logistic regression models were used to estimate the crude risk ratio and adjusted risk ratio (RR_A) of neonatal and obstetric adverse outcomes in births at GA 41⁺⁴– 42⁺⁰ weeks compared with GA 41⁺⁰– 41⁺³ weeks. The results were adjusted for relevant confounders, including induction of labor. Results: A higher incidence of neonatal morbidity and birth complications was observed in births at GA 41⁺⁴–42⁺⁰ weeks than in births at GA 41⁺⁰–41⁺³ weeks. Neonatal morbidities included an increased risk of low Apgar score (Apgar 0–6 after 5 min; RR_A 1.17, 95% confidence interval [CI] 1.01–1.34), meconium aspiration (RR_A 1.25, 95% CI 1.06–1.48), need for respiratory support (continuous positive airway pressure; RR_A 1.09, 95% CI 1.03–1.15), and a composite outcome of need for comprehensive treatment at a neonatal department or neonatal death (RR_A 1.65, 95% CI 1.29–2.11). Birth complications included emergency cesarean section (RR_A 1.17, 95% CI 1.14–1.21), severe lacerations (RR_A 1.11, 95% Cl 1.04–1.17), and increased blood loss after birth (RR_A 1.13, 95% CI 1.06–1.21). Conclusions: Births at GA 41⁺⁴–42⁺⁰ weeks were associated with an increased risk of neonatal morbidity and birth complications compared with births at GA 41⁺⁰–41⁺³ weeks. The results of this study may aid clinicians in deciding when to recommend induction of labor in late-term pregnancies.