Spina bifida is a birth defect in which the bones of the spine (vertebrae) don't form properly around the spinal cord. If it's severe, part of the spinal cord or spinal nerves may be exposed. This can cause nerve damage and lead to serious problems, so surgery may be needed soon after birth. But in most cases, the defect is mild and hidden, and it doesn't cause problems.
Spina bifida develops early in pregnancy, often before a woman knows she is pregnant. A woman can reduce her chance of having a baby with spina bifida by eating a healthy diet and taking folic acid supplements before and during pregnancy.