Spina bifida is a disorder where the spine and spinal cord do not develop properly, often resulting in paralysis and other issues. It occurs due to failure of the spine to close during the first month of pregnancy, and may be related to folic acid deficiency. Spina bifida can range from mild vertebral malformations to more severe cases where the spinal cord and membranes protrude outside the body. It affects mobility and can also cause hydrocephalus, incontinence, cognitive problems, and other health issues. The incidence is about 1 in 2000 live births for the most severe type, and 1-2 per 1000 for all types of spina bifida.