Alloimmunization by hr'(c), hemolytic disease of newborns, and perinatal management.

A study was made of hr'(c) hemolytic disease to determine its natural history and to develop criteria for its management. Anti-c is 0.52 as frequent as anti-D(Rho) in gravid women. Seventy-four percent of infants born of c-alloimmunized women mated to c-positive men show serologic evidence of hemolytic disease of newborns. Up to 40% of affected infants require transfusion. There is evidence that ABO incompatibility between mother and fetus protects against alloimmunization. Although alloimmunization is frequently related to fetomaternal bleeding, severe hemolytic disease appears to be associated with previous maternal transfusion. Maternal antiglobulin titers of less than 1:16 are usually associated with mild disease or none at all. Women with higher titers, whose mates are hr'(c)-antigen positive, are candidates for amniotic fluid pigment analysis.