The development of severe neonatal alloimmune thrombocytopenia due to anti-HPA-1a antibodies is correlated to maternal ABO genotypes

Abstract

Background. Maternal alloantibodies against HPA-1a can cross placenta, opsonize foetal platelets, and induce neonatal alloimmune thrombocytopenia (NAIT). In a study of 100, 448 pregnant women in Norway during 1995-2004, 10.6 of HPA-1a negative women had detectable anti-HPA-1a antibodies. Design and Methods. A possible correlation between the maternal ABO blood group phenotype, or underlying genotype, and severe thrombocytopenia in the newborn was investigated. Results. We observed that immunized women with blood group O had a lower risk of having a child with severe NAIT than women with group A; 20 with blood group O gave birth to children with severe NAIT, compared to 47 among the blood group A mothers (relative risk 0.43; 95 CI 0.25-0.75). Conclusion. The risk of severe neonatal alloimmune thrombocytopenia due to anti-HPA-1a antibodies is correlated to maternal ABO types, and this study indicates that the observation is due to genetic properties on the maternal side. Copyright © 2012 Maria Therese Ahlen et al.