This fact sheet uses a question-and-answer format to summarize issues related to the prevention of neural tube defects. Questions and answers address the following topics: what neural tube defects are and the most common types (spina bifida and anencephaly); occurrence of neural tube defects during the first month of pregnancy; the frequency of neural tube defects (about 2,500 each year in the United States); prevention of a neural tube defect pregnancy through the consumption of folic acid before and during pregnancy; foods which contain folic acid; people at greater risk of having low folic acid levels (smokers and users of alcohol/drugs); recommendations for folic acid supplementation for women of child-bearing age; the special importance of folic acid for women who have already had a pregnancy affected by neural tube defects; other possible causes of neural tube defects; and prenatal screening to detect neural tube defects. (DB)