Prediction of the rate of decline in fetal hemoglobin levels between first and second transfusions in red cell alloimmune disease.

OBJECTIVE: To determine variables that predict the rate of decline in fetal hemoglobin levels in alloimmune disease. METHOD: Retrospective review of singleton pregnancies that underwent first and second intrauterine transfusions for treatment of fetal anemia because of maternal Rh alloimmunization in a tertiary referral center. RESULTS: Forty-one first intrauterine transfusions were performed at 26.1 weeks (standard deviation, SD, 4.6), mean volume of blood transfused was 44.4 mL (SD 23.5) and estimated feto-placental volume expansion was 51.3% (SD 14.5%). Between first and second transfusion, hemoglobin levels reduced on average 0.40 g/dl/day (SD 0.25). Stepwise multiple regression analysis demonstrated that this rate significantly correlated with hemoglobin levels after the first transfusion, the interval between both procedures, and middle cerebral artery systolic velocity before the second transfusion. CONCLUSION: The rate of decline in fetal hemoglobin levels between first and second transfusions in alloimmune disease can be predicted by a combination of hemoglobin levels after the first transfusion, interval between both procedures, and middle cerebral artery systolic velocity before the second transfusion.