Antenatal diagnosis of placental anastomosis in a twin pregnancy using Doppler ultrasound.

Qualitative analysis of blood velocity in the umbilical arteries of twin fetuses detected by pulsed Doppler ultrasound revealed discordant patterns which permitted an accurate antenatal diagnosis of an artery-to-artery anastomosis. One twin was consistently larger than the other, had a normal umbilical artery impedance and survived; the other fetus was consistently smaller, had persistently high umbilical artery impedance and died in utero. The death of one fetus did not affect the blood flow patterns within the umbilical artery of the other up to delivery 24 h later. The case demonstrates that intrauterine morbidity due to vascular anastomoses is not confined to the transfusion of significant amounts of blood from one fetus to another.