THE EFFECT OF INTRAVASCULAR TRANSFUSION FOR SEVERELY ANEMIC FETUSES ON UMBILICAL ARTERY DOPPLER FLOW VELOCITY WAVE-FORMS

Background. To evaluate whether the doppler flow velocity waveforms re flect 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 car ried out before and after 22 diagnostic cordocentesis and 14 fetal blo od 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 (PI) (p<0.003) after cordocentesi s but not after fetal blood transfusion. There were no correlations be tween 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 change s 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 sugge st that acute changes in blood viscosity following intravascular trans fusion are not associated with an increase in resistance to flow as as sessed by doppler velocimetry. Umbilical blood sampling per se may be associated with a humorally mediated reduction in placental vascular r esistance to flow.