In a virtual repeat of its 2009 recommendation,(www.uspreventiveservicestaskforce.org) the U.S. Preventive Services Task Force (USPSTF) has released a draft statement(www.uspreventiveservicestaskforce.org) recommending that "all women planning or capable of pregnancy take a daily supplement containing 0.4 to 0.8 mg (400 to 800 µg) of folic acid" to prevent neural tube defects. This is an "A" recommendation,(www.uspreventiveservicestaskforce.org) signaling that task force members determined there is high certainty that the net benefit of providing this service is substantial.
The draft recommendation statement released on May 10 is based on a draft evidence review(www.uspreventiveservicestaskforce.org) issued the same day. Both the recommendation statement(www.uspreventiveservicestaskforce.org) and the evidence review(www.uspreventiveservicestaskforce.org) are available for public comment through June 6.
Scope and Details of the Recommendation
The draft recommendation applies to all women who are planning a pregnancy or capable of becoming pregnant. Women who previously had a pregnancy affected by a neural tube defect require special management and are outside the scope of this recommendation.
Folic acid occurs naturally in a number of foods, such as leafy greens; asparagus; broccoli and citrus fruits, including orange juice. Other foods, such as rice, pasta and many grains, are fortified with folic acid pursuant to an FDA regulation that took effect in 1998. Still, even women who consume these foods typically fail to reach the daily minimum recommended dose of 400 µg, leading USPSTF members to specifically call for oral supplementation.
- The U.S. Preventive Services Task Force has again recommended that women of childbearing age take a daily supplement containing 400 to 800 µg of folic acid to prevent neural tube defects.
- This draft recommendation applies to all women who are planning or capable of pregnancy; women who previously had a pregnancy affected by a neural tube defect are outside the scope of the recommendation.
- The two most common neural tube defects are anencephaly and spina bifida, with an estimated combined average annual prevalence of 6.5 cases per 10,000 live births.
"The task force reviewed the evidence and found that by taking a daily folic acid supplement, women who are planning to or who may become pregnant can reduce the risk of this serious type of birth defect," said USPSTF member Alex Kemper, M.D., M.P.H., in a news bulletin.(www.uspreventiveservicestaskforce.org)
Although all women of childbearing age are at risk for having a pregnancy affected by a neural tube defect and should take folic acid supplements, some factors substantially increase that risk, including
- a personal or family history of neural tube defects;
- use of certain antiseizure medications, such as valproic acid and carbamazepine;
- mutations in folate-related enzymes;
- maternal diabetes; and
Moreover, evidence suggests that some racial/ethnic groups may have a higher risk for neural tube defects. Mexican-American women, in particular, may be at increased risk because of lower consumption of folic acid-fortified foods and greater intake of corn masa-based diets.
Overall, fewer Hispanic women (17 percent) report consuming 400 µg or more of folic acid daily through fortified food or supplements compared to 30 percent of non-Hispanic white women. Hispanic women may also be at increased risk because they are more likely to have a genetic polymorphism in the methylenetetrahydrofolate reductase gene, which has been associated with decreased intracellular folate metabolism.
Given that birth prevalence rates are highest among Hispanic women, followed by non-Hispanic white and non-Hispanic black women, the implications of this heightened risk are particularly concerning.
For the current review, the USPSTF evaluated one randomized, controlled trial; two cohort studies and eight case-control studies for evidence of effectiveness of folic acid supplementation. All were deemed to be of fair quality and were supported by the findings of older fair-quality observational studies. Three of the case-control studies reviewed specifically examined the effects of folic acid supplementation by race/ethnicity.
Translation to Practice
The two most common neural tube defects are anencephaly and spina bifida, with an estimated combined average annual prevalence of 6.5 cases per 10,000 live births, according to the latest CDC data.(www.cdc.gov)
Because 50 percent of all pregnancies in the United States are unplanned, it is essential that physicians advise all women who are capable of becoming pregnant to take daily folic acid supplements. The critical period for supplementation begins one month before conception and continues through the first two to three months of pregnancy.
The AAFP, which currently mirrors the USPSTF in recommending folic acid supplementation for women of childbearing age, will evaluate the draft statement and release its own recommendation after that draft is finalized.