Neural tube defects
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* R. Brian Lowry

*   © 2005 Canadian Medical Association or its licensors

Joel Ray and associates1 report a 5-fold greater risk for neural tube defects among pregnant women of First Nations origin than among women of other ethnic groups in Ontario, after adjustment for confounding factors.

Different results were obtained in a previous study from the British Columbia Health Surveillance Registry,2 which had a much larger sample of live births and stillbirths (21 111 among First Nations mothers and 576 815 in the general population) for the 16-year period 1966 to 1981. In that study, the frequency of neural tube defects was lower in the First Nations group than the general population (1.03 v. 1.60 per 1000 total births).

In the study by Ray and associates,1 ethnicity was self-declared; furthermore, no information is provided about the father's ethnic background, the degree of First Nations genes or potential admixture with white genotypes. Such admixture has occurred in the past, so caution is needed in interpreting ethnicity (unless a detailed family history for at least 2 generations is obtained). Although that was not done for the BC study,2 only subjects known to be registered under the federal *Indian Act* (1959) and known to be registered with an Indian Band (as they were then known) were considered as First Nations. Although there have been a few instances of a white person marrying a First Nations person and thus becoming registered, the number is minuscule; we are therefore confident that in our sample both parents and probably all 4 grandparents of the babies were of First Nations background. Ethnicity is extremely important in many genetic and congenital anomaly disorders, but unfortunately it has been deemed politically incorrect to obtain this information routinely on vital statistics documents. This loss of data affects not only those who are attempting to do etiologic research but also those who might benefit from such research. 

## References

1.  1. Ray JG, Vermeulen MJ, Meier C, Cole DEC, Wyatt PR. Maternal ethnicity and risk of neural tube defects: a population-based study. CMAJ 2004; 171(4):343-5. 
    
    [Abstract/FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoiY21haiI7czo1OiJyZXNpZCI7czo5OiIxNzEvNC8zNDMiO3M6NDoiYXRvbSI7czoyMDoiL2NtYWovMTcyLzIvMTU5LmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==) 

2.  2. Lowry RB, Thunem NY, Silver M. Congenital anomalies in American Indians of British Columbia. Genet Epidemiol 1986;3:455-67.
    
    [CrossRef](http://www.cmaj.ca/lookup/external-ref?access_num=10.1002/gepi.1370030609&link_type=DOI) 
    
    [PubMed](http://www.cmaj.ca/lookup/external-ref?access_num=3803914&link_type=MED&atom=%2Fcmaj%2F172%2F2%2F159.atom)