Neural tube defects and periconceptional folic acid.

T he cause of neural tube defects (NTDs) is multi-factorial. The possibility that folic acid played a role was first reported in 1964. 1 Several clinical trials subsequently showed that the risk of recurrence and first occurrence of these abnormalities was decreased by peri-conceptional folic acid supplementation, 2–5 On the basis of these findings, supplementation of 400 µg folic acid was recommended in 1992 by the Expert Advisory Group in the United Kingdom 6 and by the US Department of Health and Human Services 7 for women in the general population while trying to conceive. Although periconceptional folic acid supplementation has been shown to be effective in randomized controlled trials , at the population level it has not been associated with any reduction in the incidence of NTDs in Western countries. 8,9 Several factors may be responsible for this observed disparity. Supplementation may not be taken at the right time. The neural tube closure occurs on days 22–28 after ovulation. Since more than 40% of pregnancies are unplanned , most of these women are unaware of being pregnant as early as 22–28 days after ovulation. In addition, the proportion of women found to have started taking folic acid supplements before conception increased from 0.8%–6.7% before 1994 to only 1%–30.6% after 1994 in the various countries studied by Rosano and coauthors. 9 It is also possible that folic acid supplements are not taken by women at highest risk of NTDs (e.g., socially disadvantaged women). Therefore, there was a campaign to increase awareness among health care professionals and the mass media for the use of folic acid before conception. A mass media campaign in the Netherlands led to an increase in preconceptional folic acid use, 10 but 25.8% of women surveyed still chose not to take the supplements even though they were aware of the beneficial effects. The main reason given was a dislike of taking drugs during pregnancy, and 63.6% said that they would prefer to take folic acid in food rather than as a tablet. Over the last few years, there have also been increasing calls for food fortification with folic acid. This approach would provide a more effective means of ensuring an adequate intake by women in high-risk groups, especially immigrant women, to whom communicating the importance of supplementation may be difficult. However, critics of such policies argued that food fortification may be associated with the masking of macrocytic …