Because of concern regarding viral disease transmission, 21 pregnant women who had been alloimmunized to various red-cell antigens donated 77 units of blood (range two to six donations) for intrauterine transfusion to their anemic fetuses. Patients received supplemental iron and vitamin therapy throughout the blood donation period. Before the first donation, the mean (+/- SD) maternal hematocrit was 34.4 +/- 2.8%, whereas at delivery it was 33.4 +/- 3.5%. Maternal hematocrit was noted to decline slightly between the first and second donations but returned to pre-donation values with subsequent donations. No adverse maternal or fetal effects occurred secondary to repeated donations. Use of maternal designated-donor red cells for intrauterine transfusion offers potential advantages over the use of random allogeneic red blood cell units.