Folic acid is one of the B vitamins. It's important in the production and development of new cells and tissues.

Folic acid is needed for the production of red blood cells. That's why a deficiency of folic acid can lead to anemia (low red blood cell count).

Doctors recommend at least 400 micrograms of folic acid daily (the amount in a standard multiple vitamin) for women who are not pregnant.

Pregnant women need 600 to 800 micrograms daily. This meets the mother's needs and the needs of her growing baby. Most prenatal vitamins contain 600 micrograms or more of folic acid.

Folic acid is also especially critical for women to take before becoming pregnant. Not having enough folic acid has been linked to certain birth defects known as neural tube defects. These occur when sections of the developing brain and spinal cord fail to close. When they are left uncovered by skin, they can become injured by direct exposure to the outside environment. This includes amniotic fluid before birth and the outside world after birth.

When the neural tube defect results in an open spinal cord (spina bifida), nerve injury to the legs, bladder and bowel may cause significant loss of function throughout life. The most severe neural tube defects leave an opening of the head/cranium (anencephaly). Anencephalic children cannot live more than a few days at most.

Taking folic acid reduces the risk of neural tube defects. Because the nervous system develops early, it is important that women take folic acid before becoming pregnant. Waiting until pregnancy to take folic acid may be too late to limit birth defects. (If you haven't been able to take folic acid before becoming pregnant, don't panic. The risk of these problems overall is still quite low, it's just that taking folic acid makes a rare problem even rarer.)

Women planning to become pregnant should take at least 400 micrograms a day of folic acid for two to three months before conception. Taking a little extra, even as much as 1000 micrograms per day is safe, especially if a woman may not be getting enough folic acid in her diet.

Women who have had a past pregnancy with a neural tube defect are at increased risk for similar problems. They should take 4000 micrograms (4 milligrams) of folic acid in the months before pregnancy.