Vaginal delivery of second twins: factors predictive of failure and adverse perinatal outcomes

Introduction: This study was performed to explore factors associated with adverse perinatal outcomes for second twins and to identify predictive factors for successful vaginal delivery of the second twin after vaginal delivery of the first twin. Methods: This 10-year retrospective study included 231 cases of twin pregnancies in which vaginal delivery of the second twin was attempted after vaginal delivery of the first twin. The relationships of obstetric characteristics with the composite adverse perinatal outcome of the second twin were analysed. Predictive factors for successful vaginal delivery of the second twin were also explored. Results: Gestational age <32 weeks was the only independent risk factor for the composite adverse perinatal outcome and neonatal intensive care unit admission for the second twin. A longer intert-win delivery interval was associated with greater risk of caesarean delivery of the second twin, but it did not increase the risk of an adverse perinatal outcome. Non-vertex presentation of the second twin at delivery was independently associated with caesarean delivery ( 9.0% vs 2.0%, P=0.03). For second twins in breech presentation, caesarean delivery was associated with the presence of less experienced birth attendants. Conclusion: Among second twins born to mothers who had attempted vaginal delivery, adverse perinatal outcomes were mainly related to prematurity. The presence of more experienced birth attendants may contribute to successful vaginal delivery of the second twin, particularly for twins in non-vertex presentation.