Spina bifida is a neural tube defect that is usually seen at birth. It happens when the neural tube, which is what forms the brain and spine, doesn't close all the way. This means the backbone doesn't form and close like it should, which leaves the spinal cord at least partially unprotected.
Spina bifida can cause both physical and intellectual disabilities, which can be mild or severe. Its effects and how serious they are depends on where the opening in the spine is, how big the opening is, and if the spinal cord and nerves are affected.
Sometimes, spina bifida can be diagnosed before a baby is born, using an ultrasound or blood test. Other times, it may not be diagnosed until after a baby is born. Treatment depends on how severe the spina bifida is.