Reference:  Williams, J., Mai, C. T., Mulinare, J., Isenburg, J., Flood, T. J., Ethen, M. & Kirby, R. S. (2015). Updated estimates of neural tube defects prevented by mandatory folic acid fortification - United States, 1995–2011. MMWR Morb Mortal Wkly Rep, 64(1), 1-5.

Research Review:  Alex X. Martinez

Spina bifida is a neural tube disorder (NTD) that occurs early during pregnancy as a result of improper closure of the embryonic tube. The development of this condition can lead to death or various degrees of disability.  In 1992, the United States Public Health Service recommended that women consume 400 µg of folic acid daily to prevent this disorder. The United States also mandated that enriched cereal grain products be fortified with 140 µg of folic acid per 100 g. As a result of mandatory fortification, the birth prevalence of NTD cases declined. It was estimated that folic acid supplementation prevents approximately 1,000 cases annually.

The purpose of this study was to provide an update of the birth prevalence of NTDs after the introduction of mandatory folic acid fortification. Data from 19 United States surveillance programs during the years 1999-2011 were studied. Prevalence of NTDs post-fortification remains relatively stable since the initial reported reduction in 1999-2000. Although the latest estimate of NTD-affected births (1,300 cases) is slightly higher, it appears that this increase can be explained by a gradual increase in the number of annual live births in the United Sates and data variations caused by differences in surveillance methodology. The data revealed that Hispanics had a higher prevalence of NTDs compared with the other racial/ethnic groups (white non-Hispanic and black non-Hispanic), while non-Hispanic blacks generally had the lowest prevalence. The surveillance programs also included anencephaly, which is another birth disorder caused by improper closure of the embryonic tube. A 28 percent reduction in prevalence was observed for anencephaly and spina bifida using data from all participating programs.

The reduction in NTD cases after the post-fortification period produced an annual savings in total direct costs of approximately $508 million. The observed reduction of NTD cases corresponds to a decrease in the prevalence of serum folate deficiency from 30 percent to less than 1 oercebt and a decrease in the prevalence of red blood cells (RBC) folate deficiency from 6 percent to no measurable deficiency. A recent study suggests that RBC folate concentrations greater than 1,000 nmol/L were sufficient to substantially attenuate the risk for NTDs at a population level. Nonetheless, 21.6 percent of women of childbearing age in the United States still do not have RBC folate concentrations associated with a lower risk for NTDs.

Health stakeholders could use the findings of this study to create interventions and strategies to maintain the consumption of folic acid in women of childbearing age or to create appropriate interventions and strategies for women with folic acid deficiency (i.e., fortified cornflower for Hispanic women). It appears that mandatory folic acid fortification remains an effective public health policy intervention.