Neonatal Mortality Rate among Twin and Singleton Births with the Gestational Age of 34-37 Weeks: A Population-Based Study

Introduction: Twin pregnancy, compared to a singleton pregnancy, is associated with a higher risk of preterm birth and other neonatal complications. This study aimed to compare neonatal mortality rates and risk factors among births with the gestational age of 34 weeks - 37 weeks in twin and singleton pregnancies. Methods: The study design was cross-sectional and population-based. We extracted the data from the birth information registry in Iran. Mothers' and neonates' information was removed from the registry systems between 2018 and 2020. We used Statistical R software to compare neonatal mortality rate, demographic variables, and risk factors between two groups of twin and singleton neonates. Results: Out of 579,873 live births with a gestational age of 34 weeks - 37 weeks, 729 (1.4/1000) singleton and 54(0.77/1000) twins (one out of two) neonates died in the delivery room in the first hour of life. Of the neonates who left the delivery room alive, 3129 (4.9 per 1000) neonates had died (5.7/1000 singleton and 3.04/1000 twin). The neonatal mortality rate in hospitalized singleton neonates (1.85%) was higher than twin group (1.06%). After adjustment of other variables, the mortality rate in twin pregnancy was significantly lower than in singletons (p value < 1/1000), with an odds ratio of 0.47 (CI: 0.39 - 0.55). Antenatal corticosteroid treatment in the twin group was significantly higher than in singletons. Conclusion: Twin neonatal mortality rate was lower than singletons in the neonates with gestational age 34 weeks - 37 weeks. Clinicians could consider these results for delivery timing in uncomplicated twin pregnancies. Antenatal corticosteroid therapy can be considered to reduce the mortality rate of late preterm neonates in resource-limited countries.