Erythroblastosis fetalis produced by anti-k.

We report an instance of transfusion-induced anti-k so severe that three intrauterine intravascular fetal transfusions were required. The pretransfusion circulating hemoglobin level in the fetus was 60 g/l and hematocrit was 0.19. This, to our knowledge, is the first example of the rare alloantibody, anti-k, producing erythroblastosis so severe that fetal transfusions were required in order to prevent hydrops fetalis from developing. Anti-k alloimmunization, which in a period of 20 years and 8 months occurred only once in 3,246 alloimmunized pregnancies in Manitoba, can cause severe fetal disease. The k-alloimmunized pregnant woman should be managed in the same manner as the D-, c-, or K-alloimmunized pregnant woman.