Folate deficiency is one of today's most common vitamin deficiencies in women. Women who consume a low level of folate during pregnancy are at risk for poor pregnancy outcomes including neural tube defects (NTD). However, other factors such as heredity, social class, maternal age, birth order, maternal diet, length of time between pregnancies, maternal zinc deficiency, use of anticonvulsant drugs, abnormal homocysteine metabolism and the use of oral contraceptives, have also been implicated as causes of NTD. Animal studies have shown that fetuses are highly dependent on the folate status of the mother. In addition, several retrospective and prospective human studies have provided evidence that folate lowers the incidence of NTD.