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Lookup NU author(s): Professor Judith RankinORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2026 The Author(s). Birth Defects Research published by Wiley Periodicals LLC. Background: Sirenomelia is a rare congenital condition most notably characterized by a single lower limb. Previous studies have suggested a prevalence of approximately 1 per 100,000 births. However, in Wales 17 cases were recorded between 1998 and 2016, suggesting a higher rate of sirenomelia in this country. Objectives: This study compared current prevalence of sirenomelia in Wales with European data. This study further reviewed detailed time, place, and person data on sirenomelia cases in Wales to investigate possible causal factors. Method: A retrospective cohort study from birth defect surveillance programs. Individual-level records for all welsh cases were examined for evidence of causal factors. Comparator data from other countries were obtained from EUROCAT (a European network of population-based registries for the epidemiological surveillance of congenital anomalies). Results: European data from 24 national and regional registries of congenital anomalies included 97 cases of sirenomelia identified across 9.6 million births between 1998 and 2016, giving a prevalence rate of 1 per 100,000 (95% CI 0.83, 1.23). Five regions reported statistically significantly higher rates than that recorded across all registries, while one region reported a significantly lower rate. Small numbers of cases limit definitive statistical interpretation. Analysis of the Wales data did not identify common epidemiological factors between cases. Conclusions: The contemporary prevalence of sirenomelia across Europe is consistent with earlier studies at approximately 1 per 100,000 births (95% CI 0.83, 1.23). However, there is greater variation between regions than would be expected by chance. There remains no definitive evidence for causal environmental factors.
Author(s): Emmerson C, Olson M, Williams C, Maddison R, Tucker D, Davies L, Perraud A, Bailey L, Humphreys C, Hughes R, Sichitiu J, Amores MO, Barisic I, Santoro M, Carbonell CC, Draper ES, Haeusler M, Monier I, Latos-Bielenska A, Dias CM, Hond ED, Ballardini E, O'Mahony M, Perthus I, Rankin J, Rissmann A, Rouget F, Stevens S, Bergman JEH, Wellesley D, Wertelecki W
Publication type: Article
Publication status: Published
Journal: Birth Defects Research
Year: 2026
Volume: 118
Issue: 5
Online publication date: 06/05/2026
Acceptance date: 24/04/2026
Date deposited: 18/05/2026
ISSN (print): 2472-1727
ISSN (electronic): 2472-1727
Publisher: John Wiley and Sons Inc.
URL: https://doi.org/10.1002/bdr2.70051
DOI: 10.1002/bdr2.70051
Data Access Statement: The data used in this study were securely provided by EUROCAT and CARIS, Public Health Wales. Requests for de-identified data should be directed to these organizations.
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