Perinatal characteristics and neonatal outcomes of singletons and twins in Chinese very preterm infants: a cohort study

BACKGROUND: The prevalence of preterm birth has been rising, and there is a paucity of nationwide data on the perinatal characteristics and neonatal outcomes of twin deliveries of very preterm infants (VPIs) in China. This study compared the perinatal characteristics and outcomes of singletons and twins admitted to neonatal intensive care units (NICUs) in China. METHODS: The study population comprised all infants born before 32 weeks in the Chinese Neonatal Network (CHNN) between January 2019 and December 2019. Three-level and population-average generalized estimating equation (GEE)/alternating logistic regression (ALR) models were used to determine the association of twins with neonatal morbidities and the use of NICU resources. RESULTS: During the study period, there were 6634 (71.2%) singletons and 2680 (28.8%) twins, with mean birth weights of 1333.70 g and 1294.63 g, respectively. Twins were significantly more likely to be delivered by caesarean section (p < 0.01), have antenatal steroid usage (p = 0.048), have been conceived by assisted reproductive technology (ART) (p < 0.01), have a higher prevalence of maternal diabetes (p < 0.01) and be inborn (p < 0.01) than singletons. In addition, twins had a lower prevalence of small for gestational age, maternal hypertension, and primigravida mothers than singletons (all p < 0.01). After adjusting for potential confounders, twins had higher mortality rates (adjusted odds ratio [AOR] 1.28, 95% confidence interval [CI] 1.10–1.49), higher incidences of short-term composite outcomes (AOR 1.28, 95% CI 1.09–1.50), respiratory distress syndrome (RDS) (AOR 1.30, 95% CI 1.12–1.50), and bronchopulmonary dysplasia (BPD) (AOR 1.10, 95% CI 1.01–1.21), more surfactant usage (AOR 1.22, 95% CI 1.05–1.41) and prolonged hospital stays (adjusted mean ratio 1.03, 95% CI 1.00–1.06), compared to singletons. CONCLUSION: Our work suggests that twins have a greater risk of mortality, a higher incidence of RDS and BPD, more surfactant usage, and longer NICU stays than singletons among VPIs in China.