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 ...