Effects of folic acid fortification on the prevalence of neural tube defects.

Objective: To analyze the effect of folic acid-fortified foods on the prevalence of neural tube defects in live newborns.
Methods: Longitudinal study with newborns from the city of Recife, Northeastern Brazil, between 2000 and 2006. Data analyzed were obtained from the Sistema Nacional de Informações de Nascidos Vivos (National Information System on Live Births). Neural tube defects were defined in accordance with the International Classification of Diseases, 10th revision (ICD-10): anencephaly, encephalocele, and spina bifida. Prevalences from the periods before (2000-2004) and after (2005-2006) the mandatory fortification period were compared. Time trend of three-month prevalences of neural tube defects were analyzed using Mann-Kendall test and Sen's Slope estimator.
Results: Tendency towards reduction in the occurrence of outcome (Mann-Kendall test; p= 0.270; Sen's Slope estimator =-0.008) was not identified in the period studied. The difference between prevalences of neural tube defects in the periods before and after food fortification with folic acid was not statistically significant, according to maternal characteristics.
Conclusions: Even though reduction in neural tube defects after the period of mandatory food fortification with folic acid was not observed, results found do not enable its benefit to prevent malformations to be ruled out. Studies assessing longer periods and considering the level of consumption of fortified products by women of fertile age are necessary.