Harmless Pregnancy-Induced Warm Autoantibodies to Red Blood Cells

BACKGROUND: There is little information concerning the development and significance of autoantibodies (aab) to red blood cells (RBCs) during pregnancy. METHODS: Unselected pregnant women were routinely screened for the presence of unexpected antibodies to RBCs using standard techniques. RESULTS: Between 2009 and 2013, 153,612 pregnant women were tested. The antibody screening test was positive in 1,721 women (1.12%). In 1,602 (1.04%) cases, immune and/or non-immune alloantibodies and cold-reactive aab were detected, whereas warm-reactive aab were found in 119 women (0.08%). In almost all cases, warm-reactive aab belonged to the IgG class. No evidence of the presence of significant haemolysis in affected women was observed. CONCLUSION: Pregnant women may rarely develop aab to RBCs, which do not appear to cause haemolytic anaemia. Further clarification is required on the reasons behind the development of these aab and their clinical insignificance.