Neural tube
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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.
Formation of the neural tube is the result of an invagination of the ectoderm following gastrulation. This process is induced by signaling molecules produced in the notochord and basal plate.
Neural tube defects
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. Taking folic acid does not completely negate the risk of neural tube problems, but markedly reduces the risk.