Maternal Rh antibody titers increased progressively in a 26 yrs old black woman at her 4th pregnancy, but the stable and low MCA PSV suggested that the fetus did not develop anemia. Hemolysis did not occur. This case describes the ability of the MCA PSV in reflecting the not crossing-over of maternal antibodies to the fetus, even in the presence of high maternal anti-D antibodies titers.

Keywords: alloimmunization, fetal anemia, middle cerebral artery peak systolic velocity