The serum transferrin receptor concentration in seven fetuses with hemolytic disease.

Six pregnant women who received intrauterine transfusions and their seven fetuses were followed during gestation. Hemoglobin concentration, hematocrit value, serum ferritin, and serum transferrin receptor (TfR) concentrations were measured. In the fetal samples, there was a tendency for the TfR concentration to decrease during gestation and after the intrauterine transfusions. Serum TfR values varied between 0.7 and 5.2 mg/L, which is near the postnatal level measured in premature infants. On the contrary, one would have expected to find highly elevated values due to the active fetal erythropoiesis. The fetal regulation of TfR production may differ from that described postnatally.