The effect of intravascular transfusion for severely anemic fetuses on umbilical artery Doppler flow velocity waveforms.

BACKGROUND

To evaluate whether the doppler flow velocity waveforms reflect the fetal hematocrit and to assess the changes of the umbilical artery doppler indices before and after the puncture of the umbilical cord.

MATERIAL AND METHODS

In this prospective-study, Pulsed-Doppler examinations of blood flow velocities in the umbilical artery were carried out before and after 22 diagnostic cordocentesis and 14 fetal blood transfusions into the umbilical vein.

RESULTS

There were decreases in the systolic/diastolic ratio (p < 0.001), the pulsatility index (PI)(p < 0.001), and the resistance index (RI)(p < 0.003) after cordocentesis but not after fetal blood transfusion. There were no correlations between the initial hematocrit and the umbilical artery doppler indices in both fetal blood transfusion group and fetal blood sampling group. There was no correlation between the increase in hematocrit and changes in umbilical artery blood-velocity waveform indices following fetal blood transfusion. The umbilical artery doppler flow-velocity indices did not predict the fetal hematocrit.

CONCLUSION

These findings suggest that acute changes in blood viscosity following intravascular transfusion are not associated with an increase in resistance to flow as assessed by doppler velocimetry. Umbilical blood sampling per se may be associated with a humorally mediated reduction in placental vascular resistance to flow.