Ultrasonography and Doppler studies in twin-to-twin transfusion syndrome

In 40 twin pregnancies, the evaluation of hemodynamics by ultrasound was performed during the period January 1986 through September 1991. The blood flow velocities' waveforms in the umbilical artery, umbilical vein and tricuspid valve, and the total cardiac dimension, were obtained by ultrasonography in conjunction with 3.5 MHz pulsed Doppler ultrasound. Six patients with twin pregnancies were identified as having twin-to-twin transfusion syndrome (TTS), on the basis of like-sex twins with monochorionic diamniotic placentation, vascular anastomosis in the placenta, and umbilical cord venous blood hemoglobin difference exceeding 5 g/dl at delivery. No distinctive findings for TTS were revealed by the measurement of umbilical artery blood flow velocity waveforms. However, cardiomegaly in 5 recipient fetuses and tricuspid regurgitation and biphasic umbilical vein waveforms in 3 recipient fetuses constituted characteristic features of TTS. Ultrasonography and a Doppler study might be beneficial in diagnosing TTS and evaluating the hemodynamics in a recipient fetus.