Concentration of anti-D antibodies in Rh(D) alloimmunized pregnant women, as a predictor of anemia and/or hyperbilirubinemia in their newborn infants

Objectives. To define a simple, safe and reliable program for the monitoring of anti-D alloimmunized pregnancies by analysis of the covariation between antenatal values of the titer and the concentration of anti-D antibodies in maternal serum, the Delta OD450 nm in amniotic fluid samples, and the levels of B-hemoglobin and S-bilirubin in the newborns at birth. Subjects. Ninety-three Rh(D) negative women with anti-D antibody titers greater than or equal to 16 who, after the completed 34th gestational week, gave birth to Rh(D) positive babies with a positive direct antiglobulin test. Methods. The titers and the concentrations of anti-D antibodies in maternal serum were determined by standard procedures every second week from the 25th week of gestation. In 47 of the 93 women, Delta OD450 nm in amniotic fluid was determined at least once. All antenatal values used in the study were determined within 14 days before delivery. Results and conclusion. Maternal serum antibody titers less than or equal to 32 or greater than or equal to 1000 could in themselves well predict unaffected and affected newborns. Antibody titers between 64 and 512 could not accurately predict newborns with or without hemolytic disease. As a complementary monitoring test, determination of the Delta OD450 nm was found to be less accurate when compared to determination of the concentration of anti-D antibodies. In order to monitor Rh(D) alloimmunized pregnancies, determination of the concentration of anti-D antibodies may possibly replace determination of Delta OD450 nm.