RESUMEN
The present study reports immunohematological data (anti-erythrocyte titer, anti-erythrocyte functional activity, percentage of sensitized erythrocytes) in 11 patients with erythroblastosis fetalis transfused in utero (IUTd). At birth it was possible to define two groups of newborns: one with low (group 1) and one with high (group 2) percentage of circulating sensitized erythrocytes, respectively. The presence of a low rate of sensitized red cells at birth in IUTd infants did not reduce the number of exchange transfusions required postnatally. On the contrary, babies of this group were affected by a more severe disease as shown by higher anti-erythrocyte maternal titer, higher anti-erythrocyte functional activity and a higher degree of fetal hemolysis. The persistence of hemolysis after birth, in spite of the absence of sensitized circulating erythrocytes, may be due to intramedullary hemolysis.