Mandatory folic acid fortification of grain products has resulted in 1,326 fewer neural tube defects among U.S. births each year, according to a report from the Centers for Disease Control and Prevention.

This estimate is one-third higher than previous calculations, which estimated that fortification averted 1,000 neural tube-affected pregnancies a year.

“Factors that could have helped contribute to the difference include a gradual increase in the number of annual live births in the United States during the postfortification period and data variations caused by differences in surveillance methodology,” Jennifer Williams of the CDC and her colleagues wrote in the Jan. 16 issue of the Morbidity and Mortality Weekly Report.

Insufficient folic acid intake increases the risk of neural tube defects, which can lead to conditions such as anencephaly and spina bifida. To address folic acid deficiencies in women, the United States mandated in 1998 that all enriched cereal grain products be fortified with 140 mcg of folic acid per 100 g.

From 1995-1996 to the postfortification period of 1999-2011, incidence of anencephaly and spina bifida declined 28% overall, with declines in neural tube defects seen for white, black, and Hispanic pregnancies. But the rates of neural tube defects were the highest among Hispanic women, potentially due to genetic factors or to insufficient folic acid intake. One strategy to reduce rates among Hispanic women would be to fortify corn masa flour, thereby averting an estimated 40 additional neural tube defects a year, the researchers wrote ( MMWR 2015;64:1-5 ).

The drop in neural tube defects carries a financial benefit, as well. Anencephaly, which is always fatal, costs an estimated $5,415 per case, and spina bifida costs an estimated $560,000 over a lifetime. Overall, the averted cases represent about $508 million in annual savings.

In addition to fortification, the CDC recommends that all women of childbearing age take 400 mcg of folic acid daily if they might become pregnant. Women with a previous neural tube defect–affected pregnancy are recommended to take a higher dose of 4 mg/day, beginning at least 4 weeks before conception and continuing through the first trimester.

The researchers reported having no financial disclosures.