Firm Evidence Favors Folic Acid

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]).