Neural tube defects.

Before the mid-1990s, about three quarters of neural tube defects could be traced to low folate levels in the mother. Since foods (mostly cereals) and prenatal vitamins now contain folate, there has been a 75% decrease in the rate of neural tube defects in the U.S. So, nowadays, the percentage of neural tube defects related to the mother's lack of folate intake is quite small, although the exact percentage has not been studied.

Folic acid.

FOlIC ACID

Alpha fetoprotein is elevated when there are neural tube defects such as spina bifida.