EXECUTIVE SUMMARY

The U.S. Preventive Services Task Force has issued a recommendation that all women who are planning or capable of pregnancy take a daily supplement containing 0.4-0.8 mg (400-800 µg) of folic acid.

  • Research indicates that daily folic acid supplementation in the periconceptional period can prevent neural tube defects, yet most women do not receive the recommended daily intake of folate from diet alone.
  • Taking folic acid before and during pregnancy can help protect babies against neural tube defects; however, the critical period when folic acid supplements provide the most protective benefits begins one month before becoming pregnant and continues through the first three months of pregnancy.

The U.S. Preventive Services Task Force (USPSTF) has just issued a recommendation that all women who are planning or capable of pregnancy take a daily supplement containing 0.4-0.8 mg (400-800 µg) of folic acid.1 Why is folic acid supplementation so important?

Neural tube defects are major birth defects of the brain and spine that occur early in pregnancy due to improper closure of the embryonic neural tube, which may lead to a range of disabilities or death. Research indicates that daily folic acid supplementation in the periconceptional period can prevent neural tube defects, yet most women do not receive the recommended daily intake of folate from diet alone.2,3

Data collected from 2003-2006 indicate that three-quarters of nonpregnant women ages 15-44 do not consume the recommended daily intake of folic acid for preventing neural tube defects.4 To update its 2009 recommendation, the USPSTF examined new evidence of the benefits and harms of folic acid supplementation in women of childbearing age.

“The task force found convincing evidence that the risk of neural tube defects can be reduced when women take a daily folic acid supplement of 400 to 800 micrograms,” says USPSTF member Alex Kemper, MD, MPH, MS, professor of pediatrics at Duke University School of Medicine and associate division chief for research in the division of children’s primary care at Duke University. “These supplements can be taken as a daily multivitamin, prenatal vitamin, or single tablet that has the recommended amount of folic acid.”

When Folic Acid is Most Critical

Taking folic acid before and during pregnancy can help protect babies against neural tube defects; however, the critical period when folic acid supplements provide the most protective benefits begins one month before becoming pregnant and continues through the first three months of pregnancy.

“Since neural tube defects occur in the first few weeks of pregnancy, it is important for women to be taking the recommended amount of folic acid before they become pregnant,” says Laura Mitchell, PhD, professor in the Department of Epidemiology, Human Genetics and Environmental Sciences, at The University of Texas Health Science Center at Houston. “Because approximately one-half of pregnancies in the United States are unplanned, the USPSTF recommendation holds for all reproductive-age women, whether or not they are planning a pregnancy, so that all pregnancies benefit from this preventive measure.”

The FDA issued a mandate for folic acid fortification of grain products, such as enriched flour and bread, in January 1998. Even with fortification, nearly one-quarter of all reproductive-age women exhibit folate levels that are sub-optimal to prevent neural tube defects.4 To help reduce the proportion of women with an inadequate intake of folic acid, the FDA in 2016 called for folic acid fortification of corn masa flour, which is used in foods such as tortillas, tacos, tortilla chips, and tamales. The addition of folic acid to corn masa flour specifically targets Hispanic women since they are at higher risk of neural tube defects than non-Hispanic women, tend to demonstrate lower blood folate levels, and consume fewer traditionally fortified foods. Despite food fortification, research indicates that women who do not take folic acid supplements are approximately three times more likely to exhibit sub-optimal folate levels compared to women who take supplements.5

“Even in the era of mandatory folic acid fortification of the food supply, taking a daily supplement remains a critical strategy for women to make sure they are receiving enough folic acid,” says Mitchell, who wrote an editorial accompanying the USPSTF’s recommendation.6

Women who present with a personal or family history of a pregnancy affected by a neural tube defect are at increased risk of experiencing a similar affected pregnancy. Some factors increase the risk of neural tube defects, including use of particular anti-seizure medications such as valproic acid or carbamazepine, maternal diabetes, obesity, and mutations in folate-related enzymes. These women may be advised to take higher doses of folic acid.6

REFERENCES

  1. US Preventive Services Task Force. Folic acid supplementation for the prevention of neural tube defects. US Preventive Services Task Force Recommendation Statement. JAMA 2017;317:183-189.
  2. Viswanathan M, Treiman KA, Kish-Doto J, et al. Folic Acid Supplementation: An Evidence Review for the US Preventive Services Task Force: Evidence Synthesis No. 145. Rockville, MD: Agency for Healthcare Research and Quality; 2017.
  3. Williams J, Mai CT, Mulinare J, et al; Centers for Disease Control and Prevention. Updated estimates of neural tube defects prevented by mandatory folic acid fortification — United States, 1995-2011. MMWR Morb Mortal Wkly Rep 2015;64:1-5.
  4. Tinker SC, Cogswell ME, Devine O, Berry RJ. Folic acid intake among U.S. women aged 15-44 years, National Health and Nutrition Examination Survey, 2003-2006. Am J Prev Med 2010;38:534-542.
  5. Tinker SC, Hamner HC, Qi YP, Crider KS. U.S. women of childbearing age who are at possible increased risk of a neural tube defect-affected pregnancy due to suboptimal red blood cell folate concentrations, National Health and Nutrition Examination Survey 2007 to 2012. Birth Defects Res A Clin Mol Teratol 2015;103:517-526.
  6. Mitchell LE. Folic acid for the prevention of neural tube defects. The US Preventive Services Task Force statement on folic acid supplementation in the era of mandatory folic acid fortification. JAMA Pediatr 2017; doi:10.1001/jamapediatrics.2016.4983.