It is customary for pregnant women to take a prenatal vitamin each day.

In theory, it might be possible for a pregnant woman to obtain the right amount of essential vitamins and minerals through a careful and complete diet. In real life, it is difficult for most women to achieve such a diet, particularly the need for Folate. It is far simpler take a prenatal vitamin each day.

Those living in nutritionally-deprived areas will particularly benefit from the addition of prenatal vitamins to their diet.

For those living in nutritionally-rich areas, it is difficult to demonstrate a large improvement in pregnancy outcome related to the taking of prenatal vitamins, with the exception of folic acid supplementation (The typical prenatal vitamin package includes 400 mcg of folic acid)  and the associated reduced risk of fetal neural tube defects.

To achieve the maximum benefit of the folic acid, many professional societies recommend women who anticipate a pregnancy initiate prenatal vitamins at least 3 months prior to conception.

For women at higher risk of having a child with a neural tube defect, many professionals recommend a higher dose of folic acid (4 mg/day, versus 400 mcg/day, or 10 times the standard dose of folic acid.) This higher dose is achieved with the use of folic acid supplements, and not by trying to take 10 prenatal vitamins a day. (10 prenatal vitamins a day could result in dangerously high levels of the other vitamins in the pill, and should not be done.)