Evaluation of the risk of umbilical cord prolapse in the second twin during vaginal delivery: a retrospective cohort study

OBJECTIVE: This study aimed to evaluate the success rate of vaginal delivery, the reasons for unplanned caesarean delivery, the rate of umbilical cord prolapse and the risk of umbilical cord prolapse in twin deliveries. DESIGN: Retrospective cohort study. SETTING: Single institution. PARTICIPANTS: This study included 455 women pregnant with twins (307 dichorionic and 148 monochorionic) who attempted vaginal delivery from January 2009 to August 2018. The following criteria were considered for vaginal delivery: diamniotic twins, cephalic presentation of the first twin, no history of uterine scar, no other indications for caesarean delivery, no major structural abnormality in either twin and no fetal aneuploidy. RESULTS: The rate of vaginal delivery of both twins was 89.5% (407 of 455), caesarean delivery of both twins was 7.7% (35 of 455) and caesarean delivery of only the second twin was 2.9% (13 of 455). The major reasons for unplanned caesarean delivery were arrest of labour and non-reassuring fetal heart rate pattern. The rate of umbilical cord prolapse in the second twin was 1.8% (8 of 455). Multivariate analysis revealed that abnormal umbilical cord insertion in the second twin (velamentous or marginal) was the only significant factor for umbilical cord prolapse in the second twin (OR, 5.05, 95% CI 1.139 to 22.472, p=0.033). CONCLUSIONS: Abnormal umbilical cord insertion in the second twin (velamentous or marginal) was a significant factor for umbilical cord prolapse during delivery. Antenatal assessment of the second twin’s umbilical cord insertion using ultrasonography would be beneficial.