The exact causes of neural tube defects are not known. Many different factors are likely to play a role, including genetics, nutrition, and environmental factors.

Research studies have found that getting enough folic (pronounced FOH-lik) acid (also known as folate or vitamin B9) before and during pregnancy can greatly reduce the risk of spina bifida and other neural tube defects.

Well-established evidence shows that women who are obese, have poorly controlled diabetes, or take certain antiseizure medications, such as phenytoin (Dilantin), carbamazepine (Tegretol), and valproic acid (Depakote), or anti-folate (such as aminopterin) are at greater risk than are other women of having an infant with spina bifida or anencephaly1, Some studies suggest that neural tube defects and miscarriage are more common among fetuses of women who experience high temperatures (such as using a hot tub or sauna or having a fever) during the first 4 to 6 weeks of pregnancy. Women who may become pregnant or who are pregnant should avoid using hot tubs or saunas.