Monoamniotic twins delivered liveborn with a forked umbilical cord.

Monoamniotic twins are rare and are associated with high intrauterine mortality rates. This case appears to represent the first report of liveborn monoamniotic monochorionic twins delivered with a bifurcated umbilical cord. Pathological and angiographic studies of the placenta demonstrated a marginally inserted two-vessel umbilical cord that bifurcated at 8.4 cm from the disk into three-vessel umbilical cords supplying each twin. This probably represents the last opportunity for cleavage of the embryo prior to the formation of conjoined twins. A review of eight prior reports of monoamniotic twins with a single, bifurcating umbilical cord is provided.