Neural tube defect (NTD)

A birth defect caused by abnormal development of the neural tube. (The neural tube is the structure present during embryonic life which gives rise to the central nervous system — to the brain and the spinal cord.) The best-known neural tube defects are anencephaly (absence of the cranial vault and absence of most or all of the cerebral hemispheres of the brain) and spina bifida (an opening in the vertebral column protecting the spinal cord), sometimes with a meningomyelocele (protrusion of the meningeal membranes that cover the spinal cord). The risk of neural tube defects can be lowered if the mother’s diet before and during pregnancy contains adequate folic acid.