Prevalence and specificity of clinically significant red cell alloantibodies in pregnant women - a study from a tertiary care hospital in Southeast Michigan

Background: Maternal red cell IgG antibodies can cross the placenta and cause hemolysis of fetal red cells in case of antigenic differences between maternal and fetal RBCs, leading to hemolytic disease of the fetus and newborn (HDFN). Although the incidence of anti-D associated HDFN has drastically reduced with Rh immune globulin prophylaxis, HDFN due to other maternal red cell alloantibodies still remains a concern. Prevalence and specificities of clinically significant red cell alloantibodies in pregnant females have rarely been reported in the USA. Methods: A retrospective chart review was conducted to determine the prevalence and specificity of clinically significant red cell alloantibodies in pregnant females who delivered at Beaumont Hospital Royal Oak between May 1, 2017 and December 31, 2017. A total of 4548 pregnant females were screened using electronic medical records. One female above 50 years age and two females with invalid ABO type were excluded from the study per IRB approved protocol. The remaining 4545 pregnant females with a valid ABO/RhD type and valid red cell antibody screen were included. Results: Out of the 4545 included females, 440 had a positive red cell antibody screen. Of these 440 females, 34 had clinically significant alloantibodies, giving an overall prevalence of 0.74%. Anti-E was the most frequently identified significant alloantibody followed by anti-K. The most prevalent significant alloantibodies in RhD positive and RhD negative females were anti-E and anti-K, respectively. Significant association (p-value <0.001) was found between RhD type and the presence of clinically significant alloantibodies amongst females with positive antibody screen. Conclusion: Our study aims to reiterate the importance of maternal red cell antibody screening during early pregnancy to help identify and manage high-risk pregnancies. Minimizing the exposure of childbearing age females to incompatible red cell antigens through unnecessary transfusions can help reduce the incidence of red cell alloimmunization and the risk of HDFN.