The predicting factors and outcomes of caesarean section of the second twin

The aim of this study was to review the indications for caesarean delivery of second twins after vaginal delivery of a first twin (combined delivery) and the associated foetal outcomes of the second twin. Possible factors that could be employed to predict combined delivery were explored. This was a retrospective review of all twin pregnancies delivered in a tertiary maternity unit between 2000 and 2013. All twins (> =24 week gestation) with vaginal delivery of the first twin were reviewed. Of a total of 1039 pairs of twins, 441 pairs had vaginal delivery of the first twin, of which 47 (10.7%) needed combined delivery. Presentation of the second twin was found to be significantly associated with combined delivery (p < .001). The odds ratio for combined delivery for breech second twin was 2.4 compared with vertex second twins while the odds ratio for transverse lie second twin was 182.8. Second twins who were delivered by combined delivery had a higher incidence of 5 min Apgar score <7. The extremely high odds ratio for combined delivery for second twins in transverse lie would probably indicate that attempts at vaginal delivery of these vertex/transverse twin pregnancies would not be worthwhile. Impact statement It remains controversial in the literature whether non-vertex second twins are associated with a higher risk for combined delivery as compared to vertex second twins. Almost all previous studies have analysed the non-vertex second twins as a whole group rather than separating them into breech presentation and transverse lie. There is only one study analysing breech presentation and transverse lie of second twin separately but it has recruited only 14 patients. To our knowledge, the cohort is the largest available dataset comparing the odds ratio for combined delivery of breech and transverse lie of the second twin separately. We found that transverse lie of the second twin have extremely high rates of combined delivery with an odds ratio 182.8 and this may be ascribed to the lack of attempts to perform internal podalic version. Combined delivery is associated with higher maternal and neonatal morbidities. With such a high risk of transverse lie second twin in having combined delivery, it appears reasonable to advise women with vertex/transverse twins not to attempt vaginal delivery unless there are obstetricians who have experience in performing internal podalic version at the time of delivery. This is useful for patient counselling regarding the decision of the mode of delivery.