How Valid Are the Rates of Down Syndrome Internationally? Findings from the International Clearinghouse for Birth Defects Surveillance and Research

Emanuele Leoncini, Lorenzo D. Botto, Guido Cocchi, Goran Anneren, Carol Bower, Jane Halliday, Emmanuelle Amar, Marian K. Bakker, Sebastiano Bianca, Maria Aurora Canessa Tapia, Eduardo E. Castilla, Melinda Csaky-Szunyogh, Saeed Dastgiri, Marcia L. Feldkamp, Miriam Gatt, Fumiki Hirahara, Danielle Landau, R. Brian Lowry, Lisa Marengo, Robert McDonnellTriphti M. Mathew, Margery Morgan, Osvaldo M. Mutchinick, Anna Pierini, Simone Poetzsch, Annukka Ritvanen, Gioacchino Scarano, Csaba Siffel, Antonin Sipek, Elena Szabova, Giovanna Tagliabue, Stein Emil Vollset, Wladimir Wertelecki, Ludmila Zhuchenko, Pierpaolo Mastroiacovo*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

28 Citations (Scopus)


Rates of Down syndrome (DS) show considerable international variation, but a systematic assessment of this variation is lacking. The goal of this study was to develop and test a method to assess the validity of DS rates in surveillance programs, as an indicator of quality of ascertainment. The proposed method compares the observed number of cases with DS (livebirths plus elective pregnancy terminations, adjusted for spontaneous fetal losses that would have occurred if the pregnancy had been allowed to continue) in each single year of maternal age, with the expected number of cases based on the best-published data on rates by year of maternal age. To test this method we used data from birth years 2000 to 2005 from 32 surveillance programs of the International Clearinghouse for Birth Defects Surveillance and Research. We computed the adjusted observed versus expected ratio (aOE) of DS birth prevalence among women 25-44 years old. The aOE ratio was close to unity in 13 programs (the 95% confidence interval included 1), above 1 in 2 programs and below 1 in 18 programs (P <0.05). These findings suggest that DS rates internationally can be evaluated simply and systematically, and underscores how adjusting for spontaneous fetal loss is crucial and feasible. The aOE ratio can help better interpret and compare the reported rates, measure the degree of under- or over-registration, and promote quality improvement in surveillance programs that will ultimately provide better data for research, service planning, and public health programs. (C) 2010 Wiley-Liss, Inc.

Original languageEnglish
Pages (from-to)1670-+
Number of pages11
JournalAmerican Journal of Medical Genetics. Part A
Issue number7
Publication statusPublished - Jul-2010


  • Down syndrome
  • epidemiology
  • prevalence
  • validity
  • registries

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