Optimal delivery timing for dizygotic twins - the short- and long-term perspective

Major obstetrics and gynecology societies offer inconsistent recommendation regarding optimal delivery timing in uncomplicated dizygotic twins. We sought to investigate the impact of delivery timing within term gestation, in dizygotic twins, on the short- and long-term offspring morbidity. A prospectively analyzed cohort of dizygotic twin deliveries was conducted. All women delivered at a regional tertiary medical center, at term (≥37 0/7), between the years 1991 and 2014, were included. The primary exposure was delivery at 37 0/7-37 + 6/7 weeks, while delivery at ≥38 0/7 weeks' gestation was considered the reference. Neonatal short- and long-term outcomes according to hospitalizations of offspring up to 18 years of age due to cardiac, respiratory, hematological, neurological, and infectious morbidity were compared. Kaplan-Meier survival curves were used to compare cumulative incidences per each major-system hospitalization. Cox regression models were used to estimate the adjusted hazard ratios, while adjusting for variables with clinical importance. During the study period, 612 dizygotic twin deliveries met the inclusion criteria. Of them, 200 (31.3%) occurred at 37-37 6/7 weeks, and 412 (68.7%) occurred at ≥38 0/7 weeks' gestation. In the long-term analysis, rates of hospitalizations involving several major morbidity categories exhibited comparable rates in both groups. The Cox regression models did not demonstrate an independent association between gestational age within term and later major pediatric morbidity in offspring (total long-term morbidity: adjusted hazard ratio 1.33, 95% confidence interval 0.77-2.29). Dizygotic twin deliveries occurring at different gestational ages within term do not appear to significantly impact on major short- and long-term outcomes.