Spina bifida is when a baby's spine and spinal cord does not develop properly in the womb, causing a gap in the spine. Spina bifida is a type of neural tube defect. The neural tube is the structure that eventually develops into the baby's brain and spinal cord. It's thought to result from a combination of genetic, nutritional and environmental risk factors, such as a family history of neural tube defects and folate (vitamin B-9) deficiency