These results support a move towards food fortification in addition to recommending use of supplements.
Trials showed, more than a decade ago, that folic acid can reduce the occurrence of neural tube defects, such as spina bifida, by half or more. Since then, many countries have tried to promote use of folic acid, either by fortifying foods or, more often, by recommending the use of supplements.
Although studies have shown that fortification of flour is effective, the impact of recommendations alone is not known.
Researchers examined data from over 13 million births in Europe and Israel from 1988 to 1998. For each country, cases of neural tube defects were identified, and policies and recommendations regarding folic acid were ascertained.
Recommendations alone did not seem to influence trends in neural tube defects, despite the proved effectiveness of folic acid. The authors estimate that thousands of pregnancies that would otherwise have been healthy were affected by neural tube defects in the study area alone since 1992.
The most likely explanation for these results is that recommendations were not implemented widely enough to produce a sustained change in behaviour in a sufficiently large proportion of women to cause measurable effects, say the authors.
These findings underscore the ongoing missed opportunities for prevention. In addition to recommending use of supplements, public health agencies and medical professionals should strongly consider implementing food fortification programmes, they conclude.