Doppler assessment of renal blood flow velocity waveforms in the anemic fetus before and after intravascular transfusion for severe red cell alloimmunization.

Image-directed pulsed Doppler ultrasonography demonstrated a decrease in the pulsatility index of the renal artery in 9 anemic fetuses (less than 30 weeks, menstrual age) soon after intravascular transfusion. The pulsatility index returned to pretransfusion values the day following the transfusion. End diastolic blood velocity in the renal artery could not be measured before the transfusion, was detectable immediately after the procedure, and was again nonmeasurable one day after the transfusion. These data suggest an increase in renal blood flow in the anemic fetus soon after intravascular transfusion to eliminate excess fluid.