B is the correct answer

The incidence of twin pregnancies in the United States has increased, with twins representing about 3% of all live births in the United States. There are three potential outcomes for the delivery of diamniotic twins: vaginal delivery of both twins, cesarean delivery for both, or vaginal delivery of twin A followed by cesarean delivery of twin B. About 75% of twins are delivered by cesarean delivery due to malpresentation of the first or second twin, maternal conditions, prematurity, or patient or physician preferences. In the United States, the most common reason for a cesarean delivery of both twins is malpresentation of twin B since many obstetricians lack knowledge and experience in performing vaginal breech deliveries.

However, breech extraction of the nonvertex second twin or internal podalic version and breech extraction of the unengaged vertex twin B is safe and effective for twins at ≥ 28 weeks gestation. Vaginal delivery of both twins is a safe option if twin A is in vertex presentation, twin B has an estimated fetal weight > 1,500 g, and the estimated fetal weight of twin B is greater than twin A with growth discordance < 20% between the twins. If there is a growth discordance ≥ 20% and twin B is the larger twin, external cephalic version can occur for twin B after vaginal delivery of twin A. This bypasses the chance of head entrapment for twin B.

To undergo trial of labor of diamniotic twins, twin A must be vertex with an estimated fetal weight of twin B ≥ 1,500 g, not< 1,500 g (A), and the pregnancy should be a minimum (C) of 28 weeks gestation to avoid the chance of head entrapment of twin B in the event of a breech vaginal delivery. Vertex-vertex presentation (D) is not necessary to offer a trial of labor for twins as long as the other criteria are met.