Delivery of the nonvertex second twin: a review of the literature.

Twin gestations comprise approximately 1 percent of all pregnancies (1), and are associated with increased perinatal morbidity and mortality, mainly due to the increased incidence of prematurity and growth restriction (2). Hazards of twin delivery can be attributed to malpresentation, most often by the second twin. The vertex-nonvertex presentation occurs in approximately 40 percent of all twins (3, 4). Although there is consensus regarding the safety of vaginal delivery for twins when both are vertex (5), controversy exists over intrapartum management when the second twin is nonvertex. Some investigators advocate cesarean delivery, particularly when the second twin is nonvertex (6), or if the expected birth weight is < 2000 gm (6-8). This review aims to determine whether vaginal delivery of the nonvertex second twin, either by breech extraction or attempted external cephalic version, is associated with increased morbidity or mortality over cesarean delivery.