The neural tube is the embryonal structure that gives rise to the brain and spinal cord. In gestation, the human neural tube gives rise to three vesicles: the rhomboencephalon , the mesencephalon and the prosencephalon.
Normally the closure of the neural tube occurs around the 30th day after fertilization. However, if something interferes and the tube fails to close properly, a neural tube defect will occur. Among the most common tube defects are anencephaly, encephalocele , and spina bifida. The incidence of neural tube defects is 2.6 in 1,000 worldwide.
Pregnant women taking medication for epilepsy have a higher chance of having a child with a neural tube defect. Research has shown that women with folic acid deficiences also have a higher chance of having a child with a neural tube defect, but this is only one factor. Folic acid is not a cure, as some women taking folic acid supplements have been known to have children with the defect.