The recommended daily intake of folic acid for all women of childbearing age is at least 400 micrograms (mcg), or 0.4 milligrams (mg). During pregnancy, the recommended dose jumps up to 600 - 800 mcg, or 0.6 - 0.8 mg, a day. If you have a family history of neural-tube defects, you should probably get 4,000 mcg (or 4 mg) of folic acid a day. Most prenatal vitamins contain the appropriate dosage of folic acid along with other vitamins that will help you stay healthy.
Women who have had their first child with a neural tube defect have a higher risk of having a second with the same defect. Healthcare providers now advise these women to take at least 4 milligrams (mg) starting one month before conception, if possible, and continuing through the first three months of pregnancy.
Talk to your doctor about how much you need before and after you conceive. Folic acid is a water-soluble vitamin, so your body will flush out the excess if you consume too much. For some women, there's an exception to this rule: Getting too much folate may hide a B-12 deficiency, sometimes a problem for vegetarians. Ask your doctor or midwife if you think you may be at risk.