A: Folic acid is the B-vitamin that can lower rates of neural tube defects. Ideally, women should take folic acid supplements prior to conception and continue during early pregnancy to help prevent these and other anatomic problems.

Women with no personal or family history of neural tube defects are advised to take 800 to 1,000 micrograms of folic acid daily. Women having a family history of neural tube defect or a prior pregnancy with a neural tube defect should take 4,000 micrograms of folic acid daily, which is equivalent to 4 milligrams. Taking more than 1,000 micrograms of folic acid is not thought to be harmful for your baby, and is encouraged in some pregnancies, including those with multiple gestations or a history of prior neural tube defects.

The main concern about folic acid is that taking high levels in adulthood can make it harder to detect a vitamin B-12 deficiency. Vitamin B-12 deficiency is more common in older adults and adults with conditions that impair food absorption. It is not usually seen in pregnant women. However, strict vegan vegetarians may be at risk of B-12 deficiencies and are advised to take B-12 supplements.

If you are not vegan, and your current diet includes meat and/or dairy products, you are unlikely to have a B-12 deficiency and choosing to take extra folic acid should not be a problem.