Typing paternal RBCs for antigens that correspond to maternal antibody may aid in the prediction of hemolytic disease of the fetus and newborn. Red cell antigen typing may also be indicated for bone marrow, tissue, organ, or blood donors prior to donation. Testing a prenatal patient for red cell antigens is generally not indicated. The occurrence of the Fya antigen is 66% in Caucasians, 10% in Blacks, and 99% in Asians. Anti-Fya can cause mild to severe (rare) hemolytic disease of the fetus and newborn. The occurrence of the Fyb antigen is 83% in Caucasians, 23% in Blacks, and 18.5% in Asians. Anti-Fyb can cause rare, mild hemolytic disease of the fetus and newborn.