Spina bifida is a birth defect that occurs when the bones in a baby’s spine do not fully form during early pregnancy. The defect can be open or closed. It can stretch the spinal cord and nerves. It sometimes exposes them to amniotic fluid, which causes permanent and progressive damage. Spina bifida occurs in about 3 to 4 babies per 10,000 live births in the U.S. Spina bifida can be mild to severe, depending on where on the spine the defect occurs.
The types of spina bifida are defined by the amount of nerve tissue exposed through gaps in the bones of the spine. The more nerve tissue that is exposed, the more severe the effects can be.
Spina bifida occulta is the mildest form of spina bifida. There is a small gap in the bones of the spine, but the skin on the back is closed. The spinal cord and the nerves are usually normal. Some people call it "hidden" spina bifida. Children can often grow into adulthood not knowing that they have this condition.
A meningocele occurs when the protective sac that covers the nerves of the spinal cord pushes out through a gap in the bones of the spine. While the sac is exposed, the nerves are usually not in the sac. This can cause mild to moderate damage to nerves that control walking as well as bowel and bladder control.
These words are used interchangeably.
Nerve tissue of the spinal cord pushes through a gap in the bones of the spine. There is no skin covering, so the nerves are exposed. This is different from a myelomeningocele (MMC) where the spinal cord comes through the bony gap.
A mass of fat under the skin attaches to the spinal cord and slowly pulls on it. This can cause the spinal cord to become “tethered” or stuck in place instead of moving freely like it normally would. While the area is covered, as a child grows, the tethered cord pulls like a rubber band. If unrepaired, this can cause nerve damage, including difficulty walking and loss of control of bowel and bladder.
Myelomeningocele (MMC) occurs when a portion of the baby’s spinal cord and surrounding nerves push through an opening in the spine. A bulging sac may be present, stretching out the spinal cord and nerves.
Spina bifida is typically found during a routine prenatal ultrasound between 18 and 22 weeks of pregnancy. A blood test can find the condition as early as 16 weeks. This test screens for maternal alpha-fetoprotein (AFP). AFP is a substance made by the baby. AFP in the mother’s blood can show if the baby may have problems.
If doctors are concerned about what they see on the ultrasound or if AFP levels are high, the mother can have more testing to confirm the diagnosis. If the mother decides to have fetal surgery, the doctors will need to perform an amniocentesis.
An amniocentesis allows the doctor to take a fluid sample from the water sac that surrounds the baby. They can test this fluid for certain markers such as AFP. This tells the doctors if spina bifida is present. It can also help determine which type of spina bifida it is.
In general, the higher the defect is on the spine, the more severe the problems may be. Depending on where the defect is on the spinal cord, the baby may have the following problems after birth:
The most serious complications of spina bifida include Chiari malformation, hydrocephalus, damage to the nerves of the spinal cord, and tethered cord.
Each case of spina bifida is unique. Open spina bifida has the most potential for getting worse as pregnancy progresses. Closed defects can often stay stable. For this reason, only open spina bifida is considered for prenatal repair, including fetoscopic repair. Less severe types of spina bifida are further evaluated by a neurosurgeon after the baby is born to decide if and when surgical repair is needed.
If a baby has an open spinal defect, the mother may be able to have surgery while they are still pregnant to repair the condition before birth. This is called fetal repair. The goal of prenatal surgery is to protect the nerves and avoid severe complications of spina bifida.
Sometimes fetal repair is not possible, either because the defect is closed or the parents decide against it. In that case, surgical repair occurs after the baby is born. This means operating on the baby within a few days after birth to close the opening in the spine. The goal is to prevent infection and further damage to the spinal cord and nerves.
How well a child with spina bifida does depends on many factors. Some children will require minimal ongoing care. Others will require medical and educational support for many years. Outcomes are usually better for babies who:
Children who receive early intervention and continued high-quality follow-up care from a team of specialists tend to have a better quality of life. They also reach a higher level of independence than those who don’t.
Last Updated 07/2025
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