Outcome of alloimmunized fetuses managed solely by cordocentesis but not requiring antenatal transfusion.

A published algorithm for the frequency of fetal blood sampling in the management of fetal hemolytic disease allows many pregnancies to continue 1-3 months after the last sample until delivery at term. Though the positive predictive value for antenatal anemia is known, the likelihood of either neonatal hyperbilirubinemia or an unexpected anemia (< 30%) is not. The perinatal records of 51 antigen-positive neonates who did not require treatment antenatally were abstracted. As fetuses, these neonates had been prospectively coded as either low risk (pattern 1), moderate risk (pattern 2) or high risk (patterns 3 and 4) for antenatal anemia (hematocrit < 30%) based on their hematocrit, reticulocyte count, and the strength of the direct Coombs' test performed on their first sample. Delivery occurred at 38 +/- 2 weeks. Neonatal complications of hemolytic disease were common. Sixty-four percent required phototherapy, 17% one or more double-volume exchange transfusions, and 13% one or more simple transfusions for late-developing anemia. In all, 29% of neonates received postnatal transfusion therapy. The only correlation between the antenatal hematologic/serologic studies and the need for postnatal transfusion therapy was the strength of the indirect Coombs' test performed on the first fetal blood sample. Two neonates unexpectedly had anemia (4% risk). In the first, the hematocrit at 35 weeks was 40% and the ultrasound 1 week later normal. In one, the algorithm had been erroneously applied. Stability of the hematocrit in fetuses at risk to develop antenatal anemia can be accurately predicted by fetal blood tests performed weeks prior to delivery.(ABSTRACT TRUNCATED AT 250 WORDS)