PROSPECTIVE NONINVASIVE MONITORING OF PREGNANCIES COMPLICATED BY RED-CELL ALLOIMMUNIZATION

Our purpose was to evaluate the impact of non-invasive assessment of f etal anemia and anti-D antibody quantification on the timing and frequ ency of invasive procedures in pregnancies complicated by rhesus alloi mmunization. Nineteen consecutive non-hydropic pregnancies referred to the fetal medicine center were assigned a prior risk category (none/m ild, moderate or severe! and monitored by: (1) serial fetal measuremen ts of umbilical vein maximal flout velocity (UVVmax), liver length and spleen perimeter measurements; and (2) serial anti-D antibody concent ration. Invasive tests for fetal anemia (amniocentesis or fetal blood sampling) were deferred in the absence of abnormal ultrasound findings and/or rising antibody levels. In six cases serial non-invasive tests were normal with stable antibody levels, and no invasive tests were p erformed; four infants were mildly affected, one was unaffected and on e required postnatal exchange transfusion. In the remaining 23 affecte d cases, amniocentesis was performed in nine cases for: elevated UVVma x alone (n = 3), elevated UVVmax and an increased antibody level (n = 2), or normal UVVmax with an increased antibody level (> 15 IU/ml) and severe prior risk category (n = 4). Six fetuses underwent fetal blood sampling (initial hematocrit 9-29%), and five of these had an elevate d UVVmax. Liver length and spleen perimeter measurements were increase d in only one anemic fetus (hematocrit 13%). Of 17 infants born alive, an elevated UVVmax prior to delivery was predictive of the need for e xchange transfusion (six of seven cases with an elevated UVVmax vs, on e of ten with a normal UVVmax; chi(2) = 5.73, p = 0.017 with Yates' co rrection). These preliminary data suggest that pregnancies with a mild or no history of fetal anemia may be monitored by a combination of se rial antibody quantification and Doppler monitoring of UVVmax.