1. Home>
2. Specialties>
3. Women's Health>
4. Summary and Comment

Firm Evidence Favors Folic Acid

Periconceptional folic acid supplementation remains key for preventing neural tube defects.

Neural tube defects are among the most common congenital anomalies in the U.S., with approximately 1 in 1000 pregnancies affected. In 1996, based on several studies (including 1 large randomized, controlled trial), the U.S. Preventive Services Task Force (USPSTF) recommended that all women who plan to conceive take daily multivitamins containing 0.4 mg to 0.8 mg of folic acid beginning 1 month before conception and that all women of childbearing age take daily supplements containing 0.4 mg of folic acid to prevent neural tube defects.

Now, the USPSTF has reviewed new observational evidence that supports its recommendation. Four studies published since 1996 showed that supplementation with multivitamins containing folic acid was associated with almost 50% fewer neural tube defects and little or no harm. Most earlier studies that posed an association between folic acid and twin pregnancies did not adequately control for fertility treatments. Folic acid supplementation is unlikely to mask vitamin B₁₂ deficiency, as this condition rarely occurs in women of childbearing age. Women who have had previous pregnancies affected by neural tube defects or who are taking certain antiepileptic drugs (e.g., valproate) are at excess risk for affected pregnancies and should take higher doses of folic acid (the American College of Obstetricians and Gynecologists recommends 4.0 mg daily [Obstet Gynecol 2003; 102:203]).

Comment: The USPSTF review of the most recent literature substantiates its 1996 recommendations: Strong evidence supports maternal folic acid supplementation (beginning at least 1 month before conception and continuing through the first 2–3 months of pregnancy) to lower risk for neural tube defects in offspring. Clinicians should recommend multivitamins that contain 0.4 mg to 0.8 mg of folic acid for all women from puberty to menopause who are at normal risk for pregnancies affected by neural tube defects; for high-risk women, daily supplements should contain 4.0 mg of folic acid.

— Wendy S. Biggs, MD

Published in Journal Watch Women's Health May 28, 2009

Citation(s):

U.S. Preventive Services Task Force. Folic acid for the prevention of neural tube defects: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med 2009 May 5; 150:626.

• Original article (Subscription may be required)
• Medline abstract (Free)

Wolff T et al. Folic acid supplementation for the prevention of neural tube defects: An update of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2009 May 5; 150:632.

• Original article (Subscription may be required)
• Medline abstract (Free)