Effects of intravascular transfusion for red cell alloimmunization on fetal arterial blood pressure

To evaluate the effects of intravascular transfusion (IVT) on the fetal umbilical arterial pressure (UAP) in pregnancies complicated by red cell alloimmunization.

UAP and amniotic fluid pressures (AFP) were measured immediately before and after IVT. Mean UAP was calculated by computing 1/3 (systolic blood pressure - diastolic blood pressure) + diastolic blood pressure. The fractional increase in fetoplacental blood volume with transfusion was calculated by dividing the net volume of blood transfused by the sum of the net volume transfused and the fetoplacental volume based on the estimated fetal weight by ultrasound. Statistical techniques included paired t-test, and the Pearson product correlation. Significance was defined as p < 0.05.

The fetal umbilical artery was punctured during a total of 27 procedures in 21 patients. Pre- and posttransfusion mean UAPs were recorded in 16 of these procedures. Mean UAP increased from 34.0 +/- 14.2 mm Hg pretransfusion to 38.6 +/- 12.8 mm Hg posttransfusion (p = 0.34). There was no correlation between the fractional change in fetoplacental blood volume and the calculated difference between pre- and posttransfusion blood pressure. Bradycardia occurred during 5 procedures (31.2%). Fetal demise occurred after 2 procedures (12.5%).

IVT appears to have a minimal effect on the fetal UAP. Fetal bradycardia occurs in a significant percentage of these cases.