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Folic Acid Supplementation for the Prevention of Neural Tube Defects: Recommendation Statement

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Folic Acid Supplementation for the Prevention of Neural Tube Defects: Recommendation Statement U.S. Preventive Services Task Force Folic Acid Supplementation for the Prevention of Neural Tube Defects: Recommendation Statement As published by the U.S. Summary of Recommendation pregnancy due to improper closure of the Preventive Services Task and Evidence Force. embryonic neural tube, which may lead to a The USPSTF recommends that all women range of disabilities or death. The most com- This summary is one in a series excerpted from the who are planning or capable of pregnancy mon neural tube defects are anencephaly (an Recommendation State- take a daily supplement containing 0.4 to underdeveloped brain and an incomplete ments released by the 0.8 mg (400 to 800 µg) of folic acid (Table 1). skull) and spina bifida (incomplete closing of USPSTF. These statements A recommendation. the spinal cord).1,2 Based on 2009-2011 data, address preventive health services for use in primary the estimated average annual prevalence of care clinical settings, Rationale anencephaly and spina bifida combined was including screening tests, IMPORTANCE 6.5 cases per 10,000 live births.1-3 Daily folic counseling, and preventive Neural tube defects are major birth defects acid supplementation in the periconceptional medications. of the brain and spine that occur early in period can prevent neural tube defects.1,2 The complete version of this statement, includ- ing supporting scientific evidence, evidence tables, Table 1. Folic Acid Supplementation for the Prevention of Neural Tube Defects: grading system, members of the USPSTF at the time Clinical Summary of the USPSTF Recommendation this recommendation was finalized, and references, Population Women who are planning or capable of pregnancy is available on the USPSTF website at http://www. Recommendation Take a daily supplement containing 0.4 to 0.8 mg (400 to 800 µg) of folic acid. uspreventiveservicestask Grade: A force.org/. Risk assessment All women of childbearing age are at risk of having a pregnancy affected by This series is coordinated neural tube defects. Some factors increase this risk, including a personal by Sumi Sexton, MD, Associate Deputy Editor. or family history of neural tube defects, use of particular antiseizure medications, maternal diabetes, obesity, and mutations in folate-related A collection of USPSTF enzymes. recommendation state- ments published in AFP is Preventive Folic acid is the synthetic form of folate, a water-soluble B vitamin. Folic acid is available at http://www. medication usually given as a multivitamin, prenatal vitamin, or single supplement, and is aafp.org/afp/uspstf. also used to fortify cereal grain products. Folate occurs naturally in foods such as dark green leafy vegetables, legumes, and oranges. However, most women do not receive the recommended daily intake of folate from diet alone. Timing The critical period for supplementation starts at least 1 month before conception and continues through the first 2 to 3 months of pregnancy. Dosage Supplementation with a multivitamin containing 0.4 to 0.8 mg (400 to 800 µg) of folic acid decreases the risk of neural tube defects. Balance of The USPSTF concludes with high certainty that the net benefit of daily folic benefits and acid supplementation to prevent neural tube defects in the developing fetus harms is substantial for women who are planning or capable of pregnancy. NOTE: For a summary of the evidence systematically reviewed in making this recommendation, the full recommenda- tion statement, and supporting documents, go to http://www.uspreventiveservicestaskforce.org/. USPSTF = U.S. Preventive Services Task Force. May 15, 2017 ◆ Volume 95, Number 10 www.aafp.org/afp American Family Physician 652A USPSTF Folic acid is the synthetic form of folate, not apply to women who have had a previous a water-soluble B vitamin (B9). Folic acid pregnancy affected by neural tube defects or is usually given as a multivitamin, prenatal who are at very high risk due to other factors vitamin, or single supplement. It is also (e.g., use of certain antiseizure medications used to fortify cereal grain products. Folate or family history). These women may be occurs naturally in foods such as dark green advised to take higher doses of folic acid. leafy vegetables, legumes, and oranges.1 However, most women do not receive the ASSESSMENT OF RISK recommended daily intake of folate from Although all women of childbearing age are diet alone.1 National Health and Nutrition at risk of having a pregnancy affected by Examination Survey (NHANES) data from neural tube defects and should take folic acid 2003 to 2006 suggest that 75% of nonpreg- supplementation, some factors increase their nant women aged 15 to 44 years do not con- risk, including a personal or family history sume the recommended daily intake of folic (first- or second-degree relative) of neural acid for preventing neural tube defects.1,2,4 tube defects.1 Women with a personal his- tory of an affected pregnancy require special RECOGNITION OF RISK STATUS care and are not within the scope of this Women who have a personal or family his- recommendation statement. Other risk fac- tory of a pregnancy affected by a neural tors include the use of particular antiseizure tube defect are at increased risk of having medications (e.g., valproic acid or carba- an affected pregnancy. However, most cases mazepine), maternal diabetes, obesity, and occur in the absence of any personal or fam- mutations in folate-related enzymes.1 ily history. Questions persist regarding increased risk of neural tube defects in some racial/ethnic BENEFITS OF PREVENTIVE MEDICATION groups. Birth prevalence rates are high- The USPSTF found convincing evidence that est among Hispanic women, followed by folic acid supplementation in the pericon- non-Hispanic white and non-Hispanic black ceptional period provides substantial benefits women.1 Genetic mutations in folate-related in reducing the risk of neural tube defects enzymes may vary by race/ethnicity. Dietary in the developing fetus. The USPSTF found folate or folic acid intake differs by race/ inadequate evidence on how the benefits of ethnicity. For example, Mexican American folic acid supplementation may vary by dos- women may be at increased risk because of age, timing relative to pregnancy, duration of decreased consumption of fortified foods therapy, or race/ethnicity. and greater intake of corn masa–based diets.1 Fewer Hispanic women (28%) report HARMS OF PREVENTIVE MEDICATION consuming 0.4 mg (400 µg) or more of folic The USPSTF found adequate evidence that acid daily through fortified food or supple- the harms to the mother or infant from folic ments, compared with 39% of non-Hispanic acid supplementation taken at the usual white women.1,5 doses are no greater than small. TIMING USPSTF ASSESSMENT Half of all pregnancies in the United States The USPSTF concludes with high certainty are unplanned.6 Therefore, clinicians should that the net benefit of daily folic acid supple- advise all women who are capable of preg- mentation to prevent neural tube defects in nancy to take daily folic acid supplements. the developing fetus is substantial for women The critical period for supplementation starts who are planning or capable of pregnancy. at least 1 month before conception and continues through the first 2 to 3 months of Clinical Considerations pregnancy.1,7,8 PATIENT POPULATION UNDER CONSIDERATION DOSAGE This recommendation applies to women who Trials and observational studies conducted are planning or capable of pregnancy. It does in settings without food fortification suggest 652B American Family Physician www.aafp.org/afp Volume 95, Number 10 ◆ May 15, 2017 USPSTF that supplementation with a multivitamin Services Task Force: Evidence Synthesis No. 145. Rock- ville, Md.: Agency for Healthcare Research and Quality; containing 0.4 to 0.8 mg (400 to 800 µg) 2017. AHRQ publication no. 14-05214-EF-1. of folic acid decreases the risk of neural 2. Williams J, Mai CT, Mulinare J, et al.; Centers for Dis- tube defects.1,7,8 Evidence shows that most ease Control and Prevention. Updated estimates of women in the United States are not con- neural tube defects prevented by mandatory folic acid fortification: United States, 1995-2011. MMWR Morb suming fortified foods in a quantity needed Mortal Wkly Rep. 2015; 64(1): 1-5. 8 to demonstrate optimal benefit. An analy- 3. Viswanathan M, Treiman KA, Kish-Doto J, Middleton sis of NHANES data found that 48% of JC, Coker-Schwimmer EJ, Nicholson WK. Folic acid respondents of childbearing age consumed supplementation for the prevention of neural tube defects: an updated evidence report and systematic the recommended amount of folic acid from review for the US Preventive Services Task Force. JAMA. mandatorily fortified foods only.1,9 2017; 317(2): 190-203. According to the National Academy of 4. Tinker SC, Cogswell ME, Devine O, Berry RJ. Folic acid intake among U.S. women aged 15-44 years, National Sciences Food and Nutrition Board, the Health and Nutrition Examination Survey, 2003-2006. tolerable upper intake level of folic acid in Am J Prev Med. 2010; 38(5): 534-542. women 19 years and older is 1 mg/d (1,000 5. Bentley TG, Willett WC, Weinstein MC, Kuntz KM. µg/d) from supplements or fortified food Population-level changes in folate intake by age, gen- der, and race/ethnicity after folic acid fortification. Am (excluding naturally occurring folate) and J Public Health. 2006; 96 (11): 2040-2047. 0.8 mg/d (800 µg/d) for those aged 14 to 18 6. Finer LB, Zolna MR. Unintended pregnancy in the years.10 Fewer than 3% of girls and women United States: incidence and disparities, 2006. Contra- aged 14 to 50 years receive more than 1 mg/d ception. 2011; 84 (5): 478-485. 7. Wolff T, Witkop CT, Miller T, Syed SB.
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