Collision and interlocking of twins.

Breech/transverse presentation of twins is highly uncommon. However, this presentation is very likely to develop into a tru collision syndrome should the mother be allowed to labor. In cases of interlocked twins in which vaginal delivery is attempted, loss of the first twin is common. Our experience, and the experience of others cited in this report, indicates that early cesarean section can prevent such a disastrous outcome. Suspicion of a collision or interlocking syndrome should be aroused in any patient carrying twins in the breech/transverse position. Abdominal delivery should be accomplished before descent of the presenting twin.