Delivery of the Breech Second Twin
About 30 or 40% of twin pregnancies result in the first twin in a head-first presentation and the second in a breech presentation. The delivery of the breech second twin is widely considered a different matter than the delivery of a single breech baby, though, some now argue that this should not be the case. Since the mother's birth canal has already been dilated by the delivery of the first twin, the passage of the second twin is less difficult. However, if the second twin is larger then the first, this would not be true.
It is common for a breech second twin to be delivered with the assistance of the obstetrician in a maneuver called breech extraction. This generally accepted procedure involves the obstetrician grasping the feet of the second twin and pulling them gently into the birth canal to initiate the breech vaginal birth. The mother's pushing efforts are also needed during this procedure.
A number of studies have shown the outcome of the breech second twin to be similar for both elective cesarean section and vaginal delivery in properly selected cases. If, however, the second twin is estimated to be considerably larger than the first twin, the risks for vaginal delivery of the breech second twin may be somewhat higher. When the first twin is in breech presentation and the second twin is in cephalic presentation, there is a small risk of a serious complication called locked twins, where the chin of the first twin becomes engaged with the chin of the second twin. This probably occurs in about 0.1% of all twin pregnancies. When locked twins is suspected, a cesarean section should be performed.