The U. S. Public Health Service and CDC recommend that all women of childbearing age consume 0.4 mg (400 micrograms) of folic acid daily to prevent two common and serious birth defects, spina bifida and anencephaly.
All women between 15 and 45 years of age should consume folic acid daily because half of U.S. pregnancies are unplanned and because these birth defects occur very early in pregnancy (3-4 weeks after conception), before most women know they are pregnant.
CDC estimates that most of these birth defects could be prevented if this recommendation were followed before and during early pregnancy.
All women who have already had an NTD-affected pregnancy should consume 0.4 mg (400 micrograms) of folic acid every day when not planning to become pregnant.
When these women are planning to become pregnant, they should consult with their health care provider about the desirability of following the August 1991 U.S. Public Health Service guideline. The guideline called for consumption of 4 milligrams (4000 micrograms) of folic acid daily beginning one month before they start trying to get pregnant and continuing through the first three months of pregnancy.
Although it appears that a lower dose, such as 0.4 milligrams, may have as great a beneficial effect as 4.0 milligrams, many health care providers recommend the higher dose. This recommendation is based on data from the most rigorous scientific study involving women who had previous pregnancies affected by neural tube defects. This dosage should be prescribed and monitored by the health care provider. Typically, a health care provider will prescribe one prenatal vitamin plus three 1 mg tablets of folic acid a day to get this dosage. Keep in mind that we do not understand all the causes of neural tube defects. We do know that most can be prevented by consuming sufficient amounts of folic acid.
Institute of Medicine (IOM) Recommendation
In 1998, the Food and Nutrition Board of the National Academy of Sciences Institute of Medicine (IOM) recommended that to reduce their risk for an NTD-affected pregnancy, women capable of becoming pregnant should take 400 micrograms of synthetic folic acid daily, from fortified foods or supplements or a combination of the two, in addition to consuming food with folate from a varied diet.
U.S. Preventive Services Task Force
The U.S. Preventive Services Task Force recommends 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. This recommendation received a Grade: A.
You may see articles and news reports on new research findings that could lead to questioning your course of action. Evidence must be strong before changes in recommendations are made by CDC. If you would like discuss some of these issues with your colleagues, we suggest joining the National Birth Defects Prevention Network listserv.