Spina bifida is a birth defect that occurs when the bones in a baby’s spine do not fully form during early pregnancy. This results in an opening on the back, usually in the mid- to lower back.  

Spina bifida can be mild to severe. The mildest form, called spina bifida occulta, usually does not cause health problems.  

The more severe types of spina bifida include myelomeningoceles, meningoceles, lipomyelomeningoceles and other less common lesions.

  • Myelomeningocele, a type of “open spina bifida,” is the most serious form of the disease. In myelomeningocele, a portion of the baby’s spinal cord and surrounding nerves protrude through an opening in the spine into an exposed, flat disc or sac that is visible on the back. This exposes the baby’s spinal cord to the amniotic fluid in the mother’s womb and can be harmful to the baby’s fetal development. Myelomeningocele is the only type of spina bifida that exposes the baby’s spinal cord to amniotic fluid.
  • Meningocele occurs when the spinal cord and nerve tissue do not protrude into the sac. In this case, the lesion is usually covered by skin.
  • A lipomyelomeningocele is a type of spina bifida in which the spinal cord in the sac is covered by fat and skin. 

Children who are born with myelomeningocele can experience serious health problems, such as hydrocephalus (an excessive accumulation of fluid in the brain) and paralysis. The severity of paralysis depends on where the opening occurs in the spine.  

Other issues that occasionally can develop in children born with a myelomeningocele include trouble breathing or swallowing. This is called the Chiari II malformation, and it occurs when the myelomeningocele affects a part of the brain called the brainstem.  

Learning disabilities, trouble with hand-eye coordination, scoliosis, sexual dysfunction and a number of other problems may develop or become noticeable as the child gets older. 

The cause of spina bifida is unknown, although some research suggests that genes, maternal diabetes, certain medications and nutrition may play a role. Spina bifida occurs in about three to four babies per 10,000 live births.