Does folic acid use help prevent birth defects?
There is good evidence that you can reduce the risk of certain birth defects (spina bifida , anencephaly, and some heart defects) by taking a daily dose of 400 micrograms folic acid before conception through the first trimester of pregnancy. Therefore, if you would like to become pregnant in the near future, you should take a multivitamin with this amount 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 each day during the month before you become pregnant until at least the 12th week of pregnancy.
Prevention of birth defects with folic acid (folate)