Maternal and neonatal characteristics of pregnancies with detected thrombocytopenia and anti-HLA class I antibodies

Abstract

Introduction: Anti-HPA 1a antibodies in connection with HPA 1a alloimmunized pregnancies have been shown to be associated with a lower birth weight in boys. The proposed mechanism for this was an affected placentation through binding of antibodies to the β3 integrin on vascular endothelial cells and/or invading throphoblasts. It was also hypothesized that thrombocytopenia could have affected placental vessel wall development. HLA class I antigens are also present on trophoblast cells and platelets, but it is not known whether anti-HLA class I antibodies could also affect foetal growth. Methods: Case control study. The case population (n=54) consisted of pregnancies with delivery of thrombocytopenic children with maternal anti-HLA class I antibodies. The control population (n=164) consisted of normal pregnancies with no clinical signs of bleeding or diagnosed thrombocytopenia. The control population was further divided into two groups: Those that tested positive for presence of anti-HLA class I antibodies in maternal samples (n=69), and those that tested negative (n=95). Results: We found significantly lower birth weight (p<0.001), lower gestational age (p=0.001), higher number of SGA children (p<0.001), increased incidence of preeclampsia (p=0.026), a higher placental weight/birth weight ratio (p<0.001), increased proportion of nulliparous mothers (p<0.001) and a higher mean optical density of anti-HLA class I antibodies (p<0.001) in the case population compared with the antibody positive control population. In comparison, there were no significant differences in variables relevant for birth weight between the two parts of the control population. Conclusion: Our data suggests that the presence of anti-HLA class I antibodies might be associated with a reduced foetal growth in the context of thrombocytopenia in the newborn.