Maternal antibodies against paternal class I human leukocyte antigens are not associated with foetal and neonatal alloimmune thrombocytopenia

The causative role of maternal, anti‐human leukocyte antigen (anti‐HLA) class I antibodies in foetal and neonatal alloimmune thrombocytopenia (FNAIT) remains controversial. Furthermore, in FNAIT cases caused by anti‐human platelet antigen‐1a (anti‐HPA‐1a) antibodies, the possible additive effect of maternal anti‐HLA class I antibodies on outcomes is unclear. Among 817 mother–father–neonate trios of suspected FNAIT, we assessed the possible association of maternal anti‐HLA class I antibodies with neonatal platelet count, and the incidence of FNAIT caused by anti‐HPA‐1a antibodies. In 144 FNAIT cases caused by anti‐HPA‐1a antibodies, we investigated the possible association of maternal anti‐HLA class I antibodies with neonatal platelet count, birth weight, and the incidence of intracranial haemorrhage (n = 16). Maternal anti‐HLA class I antibodies were not associated with neonatal platelet count in suspected cases of FNAIT. There was no significant interaction between the presence of anti‐HLA class I antibodies and anti‐HPA‐1a antibodies. In FNAIT cases caused by anti‐HPA‐1a antibodies, there was no association between the presence of anti‐HLA class I antibodies and neonatal platelet count, birth weight, or occurrence of intracranial haemorrhage. This study’s findings do not support the concept that maternal anti‐HLA class I antibodies represent a risk factor of FNAIT or disease severity.