{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T07:05:45Z","timestamp":1789369545569,"version":"build-2803163510"},"reference-count":25,"publisher":"Wiley","license":[{"start":{"date-parts":[[2026,9,13]],"date-time":"2026-09-13T00:00:00Z","timestamp":1789257600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"},{"start":{"date-parts":[[2026,9,13]],"date-time":"2026-09-13T00:00:00Z","timestamp":1789257600000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"content-domain":{"domain":["obgyn.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["BJOG"],"abstract":"ABSTRACT<\/jats:title>\n \n Objective<\/jats:title>\n Foetal\u2010neonatal alloimmune thrombocytopaenia (FNAIT) is a rare disease, most commonly caused by maternal alloantibodies to human platelet antigen (HPA)\u20101a\u00a0that can result in severe bleeding. The present study was designed to determine the frequency of higher risk for HPA\u20101a alloimmunisation and development of FNAIT among a racially and ethnically diverse cohort of pregnant women.<\/jats:p>\n <\/jats:sec>\n \n Design<\/jats:title>\n Longitudinal, prospective, non\u2010interventional, natural history study.<\/jats:p>\n <\/jats:sec>\n \n Setting<\/jats:title>\n Conducted across 28 sites in North America and Europe.<\/jats:p>\n <\/jats:sec>\n \n Population<\/jats:title>\n Pregnant women (\u2265\u200918\u2009years) with no history of FNAIT.<\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n Blood samples were collected at 10\u201314\u2009weeks' gestation and a sequential screening algorithm applied: maternal HPA\u20101a\/1b genotyping, human leukocyte antigen [HLA]\u2010DRB3*01:01 allele status, anti\u2010HPA\u20101a antibody status and foetal HPA\u20101 genotype.<\/jats:p>\n <\/jats:sec>\n \n Main Outcome Measures<\/jats:title>\n Number of women at higher risk for HPA\u20101a alloimmunisation (i.e., those who are HPA\u20101b\/b, HLA\u2010DRB3*01:01 positive, anti\u2010HPA\u20101a antibody negative and carrying an HPA\u20101a\u2010positive foetus) that alloimmunise.<\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n Of the 14\u2009114 participants screened, 1.7% were HPA\u20101b\/1b genotype, which varied according to race and geography. Of 24 women at higher risk for FNAIT, five were lost to follow\u2010up with no post\u2010partum test for alloimmunisation. At Week 10 post\u2010partum, 2\/19 higher risk participants (11%; 95% confidence interval [CI]: 1.3%, 33.1%) demonstrated anti\u2010HPA\u20101a antibodies, while 17 remained negative. Pre\u2010existing anti\u2010HPA\u20101a antibodies were identified in 18 other HPA\u20101bb, DRB3*01:01 positive women at screening.<\/jats:p>\n <\/jats:sec>\n \n Conclusions<\/jats:title>\n This prospective study confirms the rarity of a population at higher risk for HPA\u20101a alloimmunisation and FNAIT, describes the risk among Black and Asian women, and establishes a rigorous methodology to assess for risk of HPA\u20101a immunisation.<\/jats:p>\n <\/jats:sec>","DOI":"10.1111\/1471-0528.70326","type":"journal-article","created":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T06:31:13Z","timestamp":1789367473000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Population Prevalence and Incident\n HPA<\/scp>\n \u20101a Alloimmunisation in Pregnancy: A Prospective, Multi\u2010Ethnic, Natural History Study"],"prefix":"10.1111","author":[{"given":"Vasilis","family":"Sitras","sequence":"first","affiliation":[{"name":"Division of Obstetrics, Fetal Medicine Center Oslo University Hospital Oslo Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emilie","family":"Vander Haar","sequence":"additional","affiliation":[{"name":"Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology Weill Cornell Medicine\u2010New York Presbyterian Hospital New York New York USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9124-390X","authenticated-orcid":false,"given":"Russell","family":"Miller","sequence":"additional","affiliation":[{"name":"Division of Maternal Fetal Medicine Columbia University Irving Medical Center New York New York USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gwen","family":"Allen","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology St Francis Medical Center Lynnwood California USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2885-7818","authenticated-orcid":false,"given":"Sara","family":"Alson","sequence":"additional","affiliation":[{"name":"Obstetric, Gynaecological and Prenatal Ultrasound Research, Department of Clinical Sciences Lund University Lund Sweden"},{"name":"Department of Obstetrics and Gynaecology Skane University Hospital, Barnmorskestationen Roseng\u00e5rd Malmo Sweden"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Roisin","family":"Armstrong","sequence":"additional","affiliation":[{"name":"Clinical Operations, Rallybio Inc. New Haven Connecticut USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dawn","family":"Black","sequence":"additional","affiliation":[{"name":"OBGGYN Medical Center Associates Houston Texas USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael P.","family":"Bombara","sequence":"additional","affiliation":[{"name":"Clinical Operations, Rallybio Inc. New Haven Connecticut USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David","family":"Dhanraj","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology, Boonshoft School of Medicine Wright State University Dayton Ohio USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6838-2576","authenticated-orcid":false,"given":"Akash","family":"Gupta","sequence":"additional","affiliation":[{"name":"Precision Diagnostics and Therapeutics Program, Sunnybrook Health Sciences Centre and Department of Laboratory Medicine and Pathobiology University of Toronto Toronto Ontario Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4257-5553","authenticated-orcid":false,"given":"Laura","family":"Hart","sequence":"additional","affiliation":[{"name":"Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology Lewis Katz School of Medicine at Temple University Philadelphia Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7008-6477","authenticated-orcid":false,"given":"Katherine","family":"Kohari","sequence":"additional","affiliation":[{"name":"Division of Maternal Fetal Medicine, Department of Obstetrics, Gynecology, and Reproductive Sciences Yale School of Medicine New Haven Connecticut USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Laura E.","family":"Lawrence","sequence":"additional","affiliation":[{"name":"Clinical Operations, Rallybio Inc. New Haven Connecticut USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Helena","family":"Litorp","sequence":"additional","affiliation":[{"name":"Department of Women's and Children's Health Uppsala University Uppsala Sweden"},{"name":"Clinical Trial Consultants Uppsala Sweden"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hector","family":"Mendez\u2010Figueroa","sequence":"additional","affiliation":[{"name":"Division of Maternal\u2010Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences McGovern Medical School at UTHealth, the University of Texas Health Science Center Houston Texas USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Surabhi","family":"Nanda","sequence":"additional","affiliation":[{"name":"Women's Health Directorate, Department of Fetal Medicine St Thomas' Hospital London UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"Paidas","sequence":"additional","affiliation":[{"name":"Tamer Family Department of Obstetrics, Gynecology and Reproductive Sciences University of Miami Miller School of Medicine Miami Florida USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kristy","family":"Palomares","sequence":"additional","affiliation":[{"name":"Division of Maternal\u2010Fetal Medicine, Department of Obstetrics and Gynecology Saint Peter's University Hospital New Brunswick New Jersey USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5130-1514","authenticated-orcid":false,"given":"Robin","family":"Perry","sequence":"additional","affiliation":[{"name":"Division of Maternal Fetal Medicine, Department of ObGyn Cooper Medical School of Rowan University Camden New Jersey USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-5526-3082","authenticated-orcid":false,"given":"Romy","family":"Pothof","sequence":"additional","affiliation":[{"name":"Division of Fetal Medicine, Department of Obstetrics Leids Universitair Medisch Centrum Leiden the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ekkehard","family":"Schleussner","sequence":"additional","affiliation":[{"name":"Department of Obstetrics Jena University Hospital, Friedrich\u2010Schiller\u2010University Jena Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1504-0024","authenticated-orcid":false,"given":"Daniel","family":"Skupski","sequence":"additional","affiliation":[{"name":"Weill Cornell Medicine\/New York Presbyterian Queens Hospital New York New York USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eva","family":"Wiberg\u2010Itzel","sequence":"additional","affiliation":[{"name":"Department of Clinical Science and Education, Karolinska Institute S\u00f6dersjukhuset Stockholm Sweden"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shauna F.","family":"Williams","sequence":"additional","affiliation":[{"name":"Division of Maternal Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Health Rutgers New Jersey Medical School Newark New Jersey USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3250-0750","authenticated-orcid":false,"given":"Heidi","family":"Tiller","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynaecology Universitetssykehuset Nord Norge Troms\u00f8 Norway"},{"name":"Women's Health and Perinatology Research Group, Department of Clinical Medicine UiT the Arctic University of Norway Troms\u00f8 Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9343-9957","authenticated-orcid":false,"given":"Joanne","family":"Verweij","sequence":"additional","affiliation":[{"name":"Division of Fetal Medicine, Department of Obstetrics Leids Universitair Medisch Centrum Leiden the Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2884-9247","authenticated-orcid":false,"given":"James B.","family":"Bussel","sequence":"additional","affiliation":[{"name":"Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology Weill Cornell Medicine\u2010New York Presbyterian Hospital New York New York USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2026,9,13]]},"reference":[{"issue":"2","key":"e_1_2_13_2_1","doi-asserted-by":"crossref","first-page":"120","DOI":"10.1016\/j.ajog.2021.04.211","article-title":"New Developments in Fetal and Neonatal Alloimmune Thrombocytopenia","volume":"225","author":"Bussel J. 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V.Margulis N.Riera\u2010Guardia B.Calingaert et\u00a0al. \u201cFetal and Neonatal Alloimmune Thrombocytopenia: A Systematic Literature Review and Meta\u2010Analysis of Adverse Pregnancy\u2010Related Outcomes to Support the Development of a Novel Prophylactic Therapeutic \u201dAMCP Annual Meeting; April 15\u201318 (2024) New Orleans LA USA."},{"issue":"4","key":"e_1_2_13_7_1","doi-asserted-by":"crossref","first-page":"1344","DOI":"10.1111\/trf.15152","article-title":"Risk of HPA\u20101a\u2010Immunization in HPA\u20101a\u2010Negative Women After Giving Birth to an HPA\u20101a\u2010Positive Child","volume":"59","author":"Kjeldsen\u2010Kragh J.","year":"2019","journal-title":"Transfusion"},{"issue":"1","key":"e_1_2_13_8_1","first-page":"e15","article-title":"Fetal and Neonatal Alloimmune Thrombocytopenia","volume":"6","author":"Espinoza J. 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Y.","year":"2016","journal-title":"Zhonghua Yi Xue Yi Chuan Xue Za Zhi"},{"issue":"6","key":"e_1_2_13_18_1","doi-asserted-by":"crossref","first-page":"425","DOI":"10.1111\/j.1365-3148.2004.00538.x","article-title":"Real\u2010Time PCR Genotyping of Human Platelet Alloantigens HPA\u20101, HPA\u20102, HPA\u20103 and HPA\u20105 Is Superior to the Standard PCR\u2010SSP Method","volume":"14","author":"Ficko T.","year":"2004","journal-title":"Transfusion Medicine"},{"issue":"7","key":"e_1_2_13_19_1","doi-asserted-by":"crossref","first-page":"1724","DOI":"10.1111\/trf.14122","article-title":"Detection and Identification of Platelet Antibodies Using a Sensitive Multiplex Assay System\u2010Platelet Antibody Bead Array","volume":"57","author":"Metzner K.","year":"2017","journal-title":"Transfusion"},{"issue":"2","key":"e_1_2_13_20_1","doi-asserted-by":"crossref","first-page":"321","DOI":"10.1111\/j.1365-2141.1995.tb05152.x","article-title":"Antenatal Screening for Fetal Alloimmune Thrombocytopenia: The Results of a Pilot Study","volume":"90","author":"Doughty H. 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