Hematologic Observations of the Course of Erythroblastosis Fetalis

Serial studies revealed characteristic changes in the peripheral blood of infants with erythroblastosis fetalis. In the presence of elevated nucleated red cells and reticulocytosis, replacement transfusion brought about a momentary decline to normal levels followed by a second rise during the succeeding three days before the values returned to low levels. Platelet counts diminished within a day after replacement and only gradually rose toward normal after approximately three days. Such a picture was not seen in the mildly affected babies who did not receive replacement therapy, in whom the platelet values varied.

Within the first three months in both groups anemia developed in the presence of little evidence of compensating marrow activity. After a decline of the hemoglobin to an average level of 7.6 Gm. per cent, erythropoiesis became adequate for return to normal levels. This hypoplastic defect could not be correlated with any other parameter of the disease.

Abnormalities were noted in the osmotic and mechanical fragility of the red cells in this disease. The major population of cells was found to be more susceptible to osmotic stress while the limits of hemolysis were within the normal range. The osmotic curves of the blood of those patients who were not transfused returned to normal within 4 weeks. Mechanical fragility of the red cells was increased in a significant number, and this abnormality was observed until the time when minimal hemoglobin values were reached. There was no correlation of these variations in fragility with other laboratory or clinical manifestations of the disease.