- To investigate obstetrical risk factors predicting failure of vaginal delivery and an emergency cesarean section (CS) for the second twin after vaginal delivery of the first twin. In addition, the study was aimed to define perinatal outcomes of the second twin. A retrospective study was conducted, comparing all deliveries of twins in which CS was performed for the second twin to those in which both twins were delivered vaginally during the years 1988-2010. Women with multiple gestations in which a CS was performed for both twins were excluded from the study. During the study period, 1966 vaginal deliveries of the first twin were recorded; 192 involved emergency CS for the second twin. Risk factors for emergency CS of the second twin were preterm delivery, previous CS, placental abruption and breech presentation of the second twin. Perinatal outcomes did not differ between the groups. Risk factors for emergency cesarean section of the second twin are preterm delivery, previous CS, placental abruption and breech presentation. Nevertheless, short-term perinatal outcomes are comparable to twins delivered vaginally.