Strong evidence that folic acid (FA) prevents the majority of cases of neural tube defects (NTDs) has led to national organisations developing guidelines for women concerning periconceptional supplementation. In Europe, there is evidence of national variations in the incidence of NTDs, with a recent Irish study reporting an increase in the rate. This review compares the periconceptional FA supplementation guidelines between the different countries in Europe. An online search of country-specific guidelines produced before 2015 concerning periconceptional FA supplementation was conducted. If an English version was not available directly, the EUROCAT register was searched for the English version of the recommendations. We identified national guidelines from 20 European countries. Over half recommended that FA supplements be taken by women planning a pregnancy, but three recommended that they should be taken by all women of child-bearing age. Four guidelines recommended starting FA at least 4 weeks preconceptionally, but no country recommended starting FA at least 12 weeks preconceptionally as suggested by recently published studies. There is a need for further consideration of the duration of preconceptional FA supplementation specifically. The latest scientific evidence in this area should inform the development of European guidelines on FA, as there is wide variation in current recommendations. Overall, the wide variation in national guidelines concerning periconceptional FA supplementation may in part explain the differences in national rates of NTDs reported by EUROCAT. National guidelines on FA supplementation should be standardised across European countries.

Our study shows that current recommendations to prevent NTDs by FA supplementation pre-pregnancy are not being fully implemented in Ireland. We recommend a review of current public health policies on FA supplementation.

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Observed differences between under-reporters and plausible reporters suggest that the exclusion of these under-reporters represents an important potential source of bias in obesity research among women in the periconceptional period.