Late preterm births: neonatal mortality and morbidity in twins vs. singletons

Objective: To examine the outcomes of twins and singletons in the late preterm period. Materials and methods: This is a retrospective cohort study of data obtained for 165,894 births in California who delivered between 34 + 0 and 36 + 6 weeks. The primary outcome was neonatal and infant mortality. The secondary outcomes included the following neonatal morbidities: respiratory distress syndrome (RDS), intraventricular hemorrhage (IVH), necrotizing enterocolitis (NEC), seizure, and sepsis. Univariate analysis was performed using chi-square test and multivariable logistic regression was used to adjust for potential confounders. Results: There were 143,891 singleton and 22,003 twin gestations included in the study. There was no difference in the primary outcome, neonatal and infant mortality between twins and singletons delivered at 34 and 36 weeks. After controlling for multiple potential confounders, significant differences in secondary outcomes of neonatal morbidity were identified. At 34 weeks, twins had significantly higher rates of IVH (aOR 2.47 (95%CI 1.08–5.64)), NEC (aOR 2.46 (95%CI 1.42–4.29)), RDS (aOR 1.60 (95%CI 1.45–1.77)), and sepsis (aOR 1.19 (95%CI 1.05–1.34)) compared to singletons. By 36 weeks, only an increased risk of RDS persisted among twins. Conclusions: While there was no difference in mortality among twins and singletons in the late preterm period, twins may have significantly increased neonatal morbidity compared to singletons delivered between 34 + 0 and 36 + 6 weeks.