Objective To evaluate the outcome of the second twin (T2) in twins attempting a vaginal delivery. Data were collected over a 5-year period from 2004 to 2009 from the multiple pregnancy clinic at Leeds General Infirmary, UK.

Methods There were 351 twins included in the study aiming for a vaginal delivery. 78 were monochorionic and 273 were dichorionic. Gestational age below 24 weeks was excluded. Gestational age, chorionicity, parity and intertwin delivery interval were examined. Primary outcome measures were birth weight, 5 and 10 min apgar scores and neonatal admissions.

Results Adverse outcomes (depressed 5 min apgar scores and neonatal intensive care unit admissions) were observed when T2 was delivered via emergency Caesarean section following vaginal delivery of the first twin (T1). These results were observed in twins >34-week gestation, with an average intertwin delivery interval of 45.8 min. The Caesarean section rate for T2 was 2.02% (n=7). There were no significant differences in apgar scores when T2 was delivered as a vaginal breech, however admissions to the neonatal unit were increased.

Conclusion T2 is at a greater risk of adverse outcomes compared to T1 when the mode of delivery is emergency Caesarean section in conjunction with prolonged intertwin delivery interval (>20 min). This risk is independent of sex, parity, assisted conception and chorionicity. Twins delivered at <28 weeks showed depressed apgar scores in both T1 and T2.