The effect of mode of delivery in twin pregnancies on the latency period between diagnosis of preterm labor and birth

The optimal mode of delivery in twin pregnancies presenting with preterm labor is controversial. Current literature regarding these cases is based on observational studies, innately prone to bias. A possibly substantial, yet hitherto unexplored, source of bias is an effect of mode of delivery on the timing of delivery. The aim of our study is to examine whether the mode of delivery affects the latency period between preterm labor (PTL) presentation and actual delivery and to assess the possible effect of latency on neonatal outcome.A retrospective cohort study at a single tertiary center from the year 2011 to 2018. All twin pregnancies (dichorionic or monochorionic-diamniotic) between 24 and 36 weeks of gestation admitted due to PTL were included in the study.A total of 469 twin deliveries met the study criteria, of them, 204 delivered by cesarean section and 265 delivered vaginally. Cesarean delivery significantly decreased the chances of reaching a latency period of 1 or more days (OR = 0.53, 95% CI = 0.33-0.84), 2 or more days (OR = 0.47, 95% CI = 0.27-0.82) and 3 or more days (OR = 0.28, 95% CI = 0.09-0.9). In a regression model adjusting for gestational age at delivery, mode of delivery was not associated with neonatal morbidity or mortality. However, in a regression model adjusting for gestational age at PTL presentation, thereby accounting for differences in the latency period, cesarean delivery was found to significantly increase the risk of respiratory distress syndrome (OR = 1.62, 95% CI = 1.04-2.54).In PTL of twin pregnancies, the latency period is significantly longer in vaginal deliveries compared to cesarean deliveries. The possibility of longer latency period in vaginal deliveries should be considered when counseling patients on the mode of delivery in preterm twin pregnancies.