Umbilical artery Doppler flow-velocity waveforms in Rhesus-isoimmunized fetuses before and after fetal blood sampling or transfusion.

Pulsed-Doppler examinations of blood-flow velocities in the umbilical artery were carried out before and after 15 diagnostic cordocenteses and 34 fetal blood transfusions into the umbilical vein. There were decreases in the systolic/diastolic ratio (A/B) (p < 0.01), the pulsatility index (PI) (p < 0.05), and the resistance index (RI) (p < 0.01) after cordocentesis but not after fetal blood transfusion. There were no correlations between the initial hematocrit and the umbilical artery Doppler indices in the sample nor in the fetal blood sampling group. In the fetal blood transfusion group, on the other hand, there was a negative correlation between the initial hematocrit and A/B (r = -0.44; p < 0.01) and the RI (r = -0.35; p < 0.05). The umbilical artery Doppler flow-velocity indices did not predict the fetal hematocrit.