Umbilical arteriovenous malformation (AVM) is a rare congenital malformation. We report a case of umbilical AVM that was prenatally diagnosed by further color Doppler ultrasonography because of fetal cardiomegaly. At 35 weeks gestation, a male newborn was delivered by emergent cesarean section because of rapid progress of cardiomegaly and breech presentation. Three-dimensional reconstructed computed tomography after birth demonstrated the shunt was spontaneously closed. This is the first case report of umbilical AVM, which was prenatally diagnosed, and the boy was successfully delivered, suggesting that, when fetal cardiomegaly is identified, umbilical AVM must be taken into consideration.