Color and pulsed Doppler ultrasonography of reversed umbilical blood flow in an acardiac twin.

Prenatal diagnosis of an acardiac twin pregnancy was performed. At 30 gestational weeks, pulsed color Doppler ultrasound revealed polyhydramnios, reversed-pulsatile blood flow in the umbilical artery and vein of the acardiac twin, and artery-artery anastomosis on the placental surface. The total cardiac dimension, maximum blood flow velocity of the ascending aorta and the pulmonary artery in the alive twin were in the normal range.