Increased RBC autoantibody production in pregnancy

Autoimmunization against RBCs is generally believed to occur very rarely during pregnancy and to represent a high risk for those affected. The occurrence of benign RBC autoantibodies in pregnancy is reported.

The incidence of autoantibodies to RBCs in unselected pregnant and nonpregnant women were compared by the new standard gel hemagglutination method.

Data from a total of 22,782 pregnant and 12,903 nonpregnant women were analyzed. The antibody screen test was positive in 547 (2.40%) of the pregnant women. The positive test results were related to passive anti-D in 341 cases (1.50%), to clinically relevant alloantibodies in 43 cases (0.19%), to clinically irrelevant antibodies in 138 cases (0.61%), to autoantibodies in 23 cases (0.1%), and to autoantibodies plus alloantibodies in 2 cases (0.01%). In the cases of alloantibodies and/or autoantibodies, the DAT was invariably positive with anti-C3d and less commonly so with anti-IgG. The autoantibodies were first detected during pregnancy, they predominantly reacted with enzyme-treated RBCs, and none of the affected women or their infants appear to have developed clinically significant hemolysis. In the control group consisting of nonpregnant female blood donors, there were 3 cases (0.02%) of clinically insignificant IgG autoantibodies.

There is an increase in autoimmunization against RBCs during pregnancy. The resultant autoantibodies do not appear to cause significant RBC destruction. Further studies are required for precise characterization of this phenomenon.