There is good evidence that taking folic acid before and during pregnancy can reduce the risk of certain birth defects (spina bifida, anencephaly, and some heart defects).
Experts recommend taking 400 micrograms (mcg) of folic acid every day before you get pregnant through the first 3 months of pregnancy. If you are thinking about getting pregnant in the near future, you should take a multivitamin that contains 400mcg of folic acid.
Women who have had a baby with a neural tube defect will need a higher dose of folic acid. If you have had a baby with a neural tube defect, you should take 400 micrograms of folic acid every day, even when you are not planning to become pregnant. If you plan to become pregnant, you should talk to your doctor and increase your folic acid intake to 4 milligrams (mg) each day during the month before you become pregnant until at least the 12th week of pregnancy.