RESUMO
BACKGROUND: In Canada, the first recommendations on the use of folic acid (FA) supplements by women planning a pregnancy or capable of becoming pregnant were issued in 1993. In 1998, fortification of flour with FA became mandatory. The objective of this study was to assess the impact of these measures on the prevalence of neural tube defects (NTDs) in the province of Quebec. METHODS: The study population included stillbirths, live births, and elective terminations for fetal malformations that were reported in 1992-2000 for women residing in the province of Quebec. NTD cases were identified from stillbirth certificates and hospital discharge summaries. RESULTS: There was a marked decrease in the total NTD rate after 1997. The average NTD rate was 1.89 per 1000 total births during the period of 1992-1997, and 1.28 per 1000 in 1998-2000, a 32% reduction (p < 0.001). CONCLUSIONS: Fortification of flour, which began in early 1997 and gradually became widespread, is a very plausible explanation for the timing, shape, and magnitude of the decrease in NTD prevalence observed in Quebec and other Canadian provinces. An increase in FA supplement use may have played only a minor role. Birth Defects Research (Part A) 67:000-000, 2003.