Noninvasive Diagnosis by Doppler Ultrasonography of Fetal Anemia Due to Maternal Red-Cell Alloimmunization

Maternal alloimmunization occurs when a pregnant woman has an immunologic response to a paternally derived red-cell antigen that is foreign to the mother and inherited by the fetus. The antibodies may cross the placenta, bind to antigens present on the fetal erythrocytes, and cause hemolysis, hydrops fetalis, and fetal death. In the United States, the proportion of fetuses at risk for anemia because of maternal alloimmunization to red-cell antigens has been estimated to be 35 per 10,000 live births. 1 Among these at-risk fetuses, only 10 percent will require transfusion because of severe anemia 2 before 34 weeks of gestation. The remaining . . .