Neural tube defects are birth defects of the brain and spinal cord. The two most common neural tube defects are spina bifida and anencephaly. In spina bifida, the fetal spinal column doesn't close completely during the first month of pregnancy. There is usually nerve damage that causes at least some paralysis of the legs. In anencephaly, much of the brain does not develop. Babies with anencephaly are either stillborn or die shortly after birth. Getting enough folic acid , a type of B vitamin, before and during pregnancy prevents most neural tube defects. Treatments for neural tube defects vary depending on the type of defect.