[Folic acid protects against neural tube defects. But how many women of reproductive age have been informed about this fact?].

The involvement of folic acid in the aetiology of neural tube defects (NTDs) has been discussed for decades. Both observational and controlled intervention trials have shown periconceptional folic acid supplementation (PFAS) to significantly reduce the incidence both of first-time and recurrent NTDs. PFAS may also be associated with reduction in the incidence of certain other congenital malformations, preterm delivery, and intra-uterine growth retardation. However, the mechanism whereby folic acid exerts its protective effect remains unclear. Thermolabile 5,10-methyl-enetetrahydrofolate reductase was the first folate-related enzyme to be associated with an increased risk of NTDs. This genetic variant may result in increased plasma homocysteine levels, which have been linked to an increased risk of NTDs. The folate-dependent genetic variants known today can explain no more than 30-50 per cent of the observed protective effect of folate. However, available evidence suggests low maternal folate status itself to be the major determinant of NTD risk. Since the vast majority of NTDs are first occurrences, and in Sweden a large proportion of fetuses with spina bifida remain undetected at routine ultrasonography during pregnancy, primary prevention by means of PFAS represents a major potential public health asset, capable of reducing both mortality and morbidity due to NTDs. Accordingly, implementation of a national strategy to reduce the incidence of NTDs, and promote awareness among health care providers and women of reproductive age of the benefits of PFAS is strongly to be recommended. Although supplemental folic acid tablets are the best proven means of improving folate status, compliance may be a problem, which emphasises the importance of considering a nutrient fortification programme as a complementary strategy for reducing the incidence of NTDs.