Because NTDs originate in the first month of pregnancy, before many women know they are pregnant, it is important for a woman to have enough folic acid in her system before conception. Folic acid is recommended for all women of childbearing age because about half of all pregnancies in the United States are unplanned (1).
Why should women of childbearing age take folic acid?
Studies show that if all women consumed the recommended amount of folic acid before and during early pregnancy, up to 70 percent of all NTDs could be prevented (1, 2).
The neural tube is the embryonic structure that develops into the brain and spinal cord. This structure, which starts out as a tiny ribbon of tissue, normally folds inward to form a tube by the 28th day after conception. When this process goes awry and the neural tube does not close completely, defects in the brain and spinal cord can result. In the United States, about 2,200 babies are born with NTDs each year, and many other affected pregnancies end in miscarriage or stillbirth (3).
The most common NTDs are spina bifida and anencephaly. Spina bifida, often called “open spine,” affects the backbone (spine) and, sometimes, the spinal cord. Children with the severe form of spina bifida have some degree of leg paralysis and bladder and bowel control problems and, sometimes, additional neurologic and developmental problems. Anencephaly is a fatal condition in which a baby is born with a severely underdeveloped brain and skull.
Studies suggest that folic acid may help prevent some other birth defects, including cleft lip and palate and some heart defects (1, 4).
How much folic acid does a woman need?
The March of Dimes recommends that all women who can become pregnant take a multivitamin that contains 400 micrograms of folic acid every day starting before pregnancy, as part of a healthy diet. This advice, based on recommendations from the Institute of Medicine (IOM) (5), assures that a woman can get all the folic acid and other vitamins she needs daily. A 2007 March of Dimes Gallup survey showed that 40 percent of women of childbearing age in the United States take a vitamin with folic acid daily (6).
A healthy diet includes foods that are fortified with folic acid and foods that contain folate, the natural form of folic acid that is found in foods. Many grain products in the United States are fortified with folic acid. This means that a synthetic (manufactured) form of folic acid is added to them. Enriched flour, rice, pasta, bread and cereals are examples of fortified grain products (check the label to see if a product is enriched). Folate-rich foods include leafy green vegetables, dried beans, legumes, oranges and orange juice.
Folic acid from vitamin supplements and fortified foods is more readily absorbed and made available for use by the body than natural folate from food. According to the IOM, the body absorbs about 50 percent of food folate. By contrast, the body absorbs approximately 85 percent of the folic acid in fortified foods and 100 percent of the folic acid in a vitamin supplement (5). Cooking and storage can destroy some of the folate in foods.
Numerous studies have shown that the synthetic form of folic acid helps prevent NTDs. The IOM, the Centers for Disease Control and Prevention (CDC), and the March of Dimes recommend that women who could become pregnant consume 400 micrograms a day of the synthetic form of folic acid (1, 5). Women can get this amount by taking a multivitamin or eating a serving of cereal that contains 100 percent of the daily value (DV) of folic acid (400 micrograms) (1). Most multivitamins and about 50 breakfast cereals contain this amount in one serving (7). Other cereals contain only 25 percent of the recommended amount, so it is important to check the label on the box.
Do women need folic acid throughout pregnancy?
Yes. A woman may need more folic acid later in pregnancy than she did in the early weeks. The IOM recommends that women increase their intake of folic acid to 600 micrograms a day (from supplements and food sources) once their pregnancy is confirmed (5). Most health care providers recommend a prenatal vitamin, most of which contain 800 to 1,000 micrograms of folic acid. However, women should not take more than 1,000 micrograms (or 1 milligram) without their provider's advice (1, 5).
Do some women need more folic acid?
If a woman has already had a pregnancy affected by an NTD, she should consult her provider before her next pregnancy about the amount of folic acid she should take. Studies have shown that taking a larger dose of folic acid daily (4,000 micrograms, which equals 4 milligrams), beginning at least one month before pregnancy and in the first trimester of pregnancy, reduces by about 70 percent the risk of having another affected pregnancy (8). Women should take only one prenatal vitamin, plus three 1-milligram folic acid tablets to get the right amount (8). Taking more than one prenatal vitamin may cause women to get too much of certain other vitamins, such as vitamin A.
Women with diabetes, epilepsy and obesity are at increased risk of having a baby with an NTD (1). Women with these disorders should consult their providers before pregnancy to see if they should take a larger dose of folic acid.
How much folic acid is in fortified foods?
Since January 1, 1998, the U.S. Food and Drug Administration (FDA) has required the addition of 140 micrograms of folic acid per 100 grams of grain to cereals, breads, pastas and other foods labeled “enriched.” This fortification makes it easier for women to get folic acid from their diets. Studies show that fortification is associated with increased blood folate levels in women of childbearing age (9). Since fortification of grain products, the rate of NTDs in the United States has decreased by one-third, although other factors have contributed to this decline (10). Women of childbearing age should keep in mind that the amount of folic acid added to fortified foods (with the exception of some cereals) is small, and most women cannot get enough daily folic acid from their diet alone.
When the FDA determined that folic acid should be added to fortify grains, the FDA limited the amount to be added because of the potential concern that high levels of folic acid might mask a vitamin B-12 deficiency (11). This condition is called pernicious anemia and is seen mainly in elderly people. Very high doses of folic acid (more than 1,000 micrograms a day) may correct the anemia caused by the vitamin deficiency, but not the deficiency itself, and cause its diagnosis to be delayed. Left untreated for an extended period of time, the vitamin B-12 deficiency can cause irreversible nerve damage. To date, research has not demonstrated any risk of pernicious anemia with folic acid fortification. Many experts, including the March of Dimes and the American Medical Association (AMA), believe that the level of fortification can be safely increased without risk to the public's health (12).
How does folic acid prevent birth defects?
How folic acid prevents NTDs is not well understood. Most studies suggest that it may correct a nutritional deficiency. However, others suggest that supplemental folic acid may help people compensate for common genetic traits that make them relatively inefficient in using dietary folate. These traits could put women at extra risk for NTDs in offspring (13).
Besides helping to prevent certain birth defects, folic acid plays other important roles during pregnancy. A pregnant woman needs extra folic acid to help her to produce additional blood cells. Folic acid also supports the rapid growth of the placenta and fetus and is needed to produce new DNA (genetic material) as cells multiply. Without adequate amounts of folic acid, cell division could be impaired, possibly leading to poor growth in the fetus or placenta. Studies suggest that women who are deficient in folic acid may be more likely to have a premature baby (14).
Does folic acid have other health benefits?
Folic acid is important for everyone in maintaining health. It has long been known that folic acid plays an important role in the production of normal red blood cells, and that individuals who are deficient in folic acid sometimes develop a form of anemia called megaloblastic anemia (characterized by a reduced number of red blood cells).
Folic acid also may play a role in preventing other health problems.
Is the March of Dimes supporting research on folic acid?
The March of Dimes has supported a number of research grants aimed at improving understanding of how folic acid prevents NTDs. A current grantee is seeking to determine whether women who have a gene mutation that results in a deficiency of folic acid are at increased risk of preterm delivery, with the goal of identifying and treating these women and helping to prevent preterm births.
Another is investigating whether maternal deficiency of folic acid during critical stages of pregnancy may affect imprinted genes (those that act differently depending on whether they are inherited from the father or mother), possibly leading to susceptibility to chronic diseases such as diabetes, heart disease and cancer. If so, it may be possible to develop nutritional interventions that may help reduce the risk of chronic diseases.
For more information
For more information about folic acid, see Questions and Answers.
The March of Dimes is a member of the National Council on Folic Acid, a collaborative group of health organizations whose mission is to improve health by promoting the benefits and consumption of folic acid.
The Grain Foods Foundation is a national sponsor of March of Dimes March for Babies. The foundation is committed to raising awareness about the important role that B vitamins and folic acid, in particular, play in preventing birth defects.
References- Centers for Disease Control and Prevention (CDC). Folic Acid: Frequently Asked Questions. Updated 11/16/05, accessed 11/2/06.
- Berry, R.J., et al. Prevention of Neural Tube Defects with Folic Acid in China. New England Journal of Medicine, volume 341, number 20, November 11, 1999, pages 1485-1490.
- Mercereau, P., et al. Spina Bifida and Anencephaly Before and After Folic Acid Mandate—United States, 1995-1996 and 1999-2000. Morbidity and Mortality Weekly Report, volume 53, number 17, May 7, 2004, pages 362-365.
- Botto, L.D., et al. Vitamin Supplements and the Risk for Congenital Anomalies Other Than Neural Tube Defects. American Journal of Medical Genetics C Semin. Med. Genet., volume 125, number 1, February 15, 2004, pages 12-21.
- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes: Folate, Other B Vitamins, and Choline. Washington, DC, National Academy Press, April 17, 1998.
- Gallup Organization and March of Dimes Foundation. Improving Preconception Health: Women's Knowledge and Use of Folic Acid. White Plains, NY, March of Dimes, December 2007.
- Centers for Disease Control and Prevention (CDC). Cereals that Contain 100% of the Daily Value (DV) of Folic Acid. Updated 8/04, accessed 11/2/06.
- Centers for Disease Control and Prevention (CDC). Folic Acid: PHS Recommendations. Updated 7/25/05, accessed 11/2/06.
- Centers for Disease Control and Prevention (CDC). Folate Status in Women of Childbearing Age, by Race/Ethnicity—United States, 1999-2000. Morbidity and Mortality Weekly Report, volume 51, number 36, September 13, 2002, pages 808-810.
- Williams, L.J., et al. Decline in the Prevalence of Spina Bifida and Anencephaly by Race/Ethnicity: 1995-2002. Pediatrics, vol. 116, number 3, September 2005, pages 580-586.
- U.S. Food and Drug Administration. Folic Acid Fortification Fact Sheet. February 29, 1996.
- American Medical Association (AMA). AMA Report 6 of the Council on Science and Public Health (A-06): Folic Acid Fortification of Grain Products. June 22, 2006.
- Kirke, P.N., et al. Impact of the MTHFR C677T Polymorphism on Risk of Neural Tube Defects: Case Control Study. British Medical Journal, volume 328, June 25, 2004, pages 1851-1857.
- Siega-Riz, A.M., et al. Second Trimester Folate Status and Preterm Birth. American Journal of Obstetrics and Gynecology, volume 191, 2004, pages 1851-1857.
November 2006 (R 3-08)
