Spina bifida is a type of birth defect that causes abnormal formation of the spinal column.

What is going on in the body?

The spinal column is a series of bones stacked on top of each other. There is a canal, or opening, in the center of these bones. This canal contains the spinal cord, a protective membrane around the cord, and many nerves. In spina bifida, the rear part of the spinal canal does not develop properly. This leaves an opening in the spinal column, which may cause problems in the nervous system. This most often occurs in the lower back, but any part of the spinal column may be affected. There are three common forms of spina bifida.

Spina bifida occulta is the most common and least severe form of spina bifida. The rear part of the spinal column usually has only a small opening. The spinal cord and the protective membrane usually remain in their proper place.

Meningocele is the least common of the three forms. The rear part of the spinal column has a larger opening. The protective membrane around the cord sticks out through the spinal column. The spinal cord and nerves usually remain in place.

Myelomeningocele is the most severe form of this condition. The rear part of the spinal cord has a larger opening. The protective membrane and the spinal cord or some nerves stick out through the opening.

Some children with spina bifida have hydrocephalus, or an increase in the fluid surrounding the brain.

What are the causes and risks of the condition?

Both genes and the environment are thought to play a part in causing spina bifida. For example, Caucasian women have affected children more often than African American women. The following factors increase the risk of a woman having a child with spina bifida: