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CC BY 4.0 · Ultraschall Med
DOI: 10.1055/a-2773-2240
Original Article

Causes and outcomes of prenatally unexplained fetal anemia

n/a

Authors

  • Saja Anabusi

    1   Fetal Medicine Unit, Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, Canada (Ringgold ID: RIN22494)
    2   Maternal Fetal Medicine Unit, Department of Obstetrics and Gynaecology, Saint John Regional Hospital, Saint John, Canada (Ringgold ID: RIN72881)

  • Charles Litwin

    3   Fetal Medicine Unit, Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, Canada

  • Greg Ryan

    3   Fetal Medicine Unit, Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, Canada
    4   Maternal-Fetal Medicine, Ontario Fetal Centre, Toronto, Canada (Ringgold ID: RIN574860)

  • David Chitayat

    5   The Prenatal Diagnosis and Medical Genetics Program, Department of Obstetrics and Gynecology, Mount Sinai Hospital, Toronto, Canada
    6   Division of Clinical and Metabolic Genetics, Department of Pediatrics, The Hospital for Sick Children, Toronto, Canada (Ringgold ID: RIN7979)
    7   Department of Genetics, Ontario Fetal Centre, Toronto, Canada (Ringgold ID: RIN574860)

  • Shiri Shinar

    3   Fetal Medicine Unit, Department of Obstetrics and Gynaecology, Mount Sinai Hospital, Toronto, Canada
    8   Department of Obstetrics and Gynaecology, Ontario Fetal Centre, Toronto, Canada (Ringgold ID: RIN574860)
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Purpose: Despite advances in diagnostic approaches, fetal anemia of unknown etiology continues to be observed in rare cases. This study aimed to assess the incidence of unexplained fetal anemia and to evaluate the associated perinatal outcomes. Materials and Methods: We conducted an observational retrospective cohort study of all fetuses who underwent fetal blood sampling (FBS) due to an MCA PSV>1.5 MoM at a tertiary center between 2007 and 2024. Fetuses were included if they had moderate or severe anemia defined as a hemoglobin (Hgb) deviation of more than 20 g/L below a gestational age adjusted mean, with a negative anemia workup. Prenatal and postnatal outcomes were obtained. Results: Among 376 fetuses that underwent fetal blood sampling for anemia, 361 (96%) had an identified cause, while 15 (4%) had moderate to severe anemia of unknown etiology. Seven fetuses presented with non-immune hydrops and eight with other major structural anomalies not typically associated with anemia. Eleven (73%) of the 15 fetuses with unexplained anemia had thrombocytopenia, with platelets below 100,000/µL in 8 cases and below 50,000/µL in 6 cases. Seven cases (47%) resulted in perinatal death. Rare causes of anemia were elucidated only in 5 cases (33%) postnatally despite extensive investigations. Conclusion: Unexplained fetal anemia is uncommon and associated with poor neonatal outcomes warranting close pre- and postnatal surveillance.



Publication History

Received: 10 September 2025

Accepted after revision: 15 December 2025

Accepted Manuscript online:
15 December 2025

© . The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/).

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