Abstract Background Fetal/neonatal alloimmune thrombocytopenia (FNAIT) caused by antibodies to human platelet antigen (HPA)‐1a in white HPA‐1a‐negative mothers is the most frequent cause of intracranial hemorrhage (ICH) in otherwise healthy newborns. Aims To investigate the natural history of FNAIT and establish a biobank from HPA‐1a‐negative alloimmunized and nonimmunized pregnancies. Methods A total of 24,259 pregnant women were recruited to the study during 2013–2017 and 24,236 were screened for HPA‐1a. Anti‐HPA‐1a antibodies were tested by Monoclonal Antibody Immobilization of Platelet Antigens (MAIPA) and some samples (MAIPA‐negative), with Luminex bead‐based immunoassay (PAKLx) if the neonate had thrombocytopenia and/or ICH. HPA‐1 genotyping of fathers, fetuses (from maternal plasma), and newborns was performed. Biological material was stored in biobanks in Norway and Poland. Results Among 583/24,236 (2.4%) HPA‐1a‐negative women, samples were obtained from 529, of which 513 were examined during pregnancy. Anti‐HPA‐1a antibodies were detected in 48/529 (9.1%) women; whereof 34/513 (6.6%) during pregnancy, either by prospective MAIPA ( n = 27) or in retrospect by PAKLx in MAIPA‐negatives ( n = 7). FNAIT was diagnosed in 11/34 (32%) neonates from alloimmunized pregnancies: in 6/11 cases by prospective MAIPA and in 5/11 by retrospective PAKLx. There were no neonates with FNAIT‐associated ICH delivered by MAIPA‐positive women, but 3 ICH/severe thrombocytopenia cases were diagnosed by PAKLx. Among nonimmunized HPA‐1a‐negative women, 28 newborns had thrombocytopenia and 2 others had ICH. Conclusions Feasibility of HPA‐1 antenatal screening was demonstrated, and a comprehensive biobank was established. The FNAIT detection rate was improved by retrospective diagnostics by PAKLx, including 3 newborns with ICH not identified by prospective MAIPA.
Katarzyna et al. (Fri,) studied this question.