No one knows every cause of spina bifida. Researchers believe it comes from a mix of genes and environment, and they have identified several factors that raise the risk. The most important one, low folic acid, is also the one you can do the most about.

The short version

  • What it is: A birth defect where the spine and spinal cord don’t form or close completely in the first month of pregnancy. It affects about 1 in every 2,857 U.S. births, according to the CDC.
  • Known risk factors: not getting enough folic acid, certain medicines, diabetes that isn’t well controlled, obesity, overheating or fever early in pregnancy, and a family history of neural tube defects.
  • Biggest prevention step: 400 mcg of folic acid every day, starting at least one month before pregnancy.
  • Many babies with spina bifida are born into families with no history of it, so prevention applies to everyone who could become pregnant.

What spina bifida is

Spina bifida is a type of neural tube defect. In the first month of pregnancy, a structure called the neural tube forms and closes to become the baby’s brain and spinal cord. When part of it doesn’t close all the way, the backbone around the spinal cord doesn’t close either, which often damages the spinal cord and nerves, according to the CDC.

It can happen anywhere along the spine, and severity ranges widely. The CDC describes three main types:

Type What happens Typical effect
Myelomeningocele A fluid-filled sac pushes through an opening in the baby’s back, with part of the spinal cord and nerves inside it The most serious type. Causes moderate to severe disabilities, such as not being able to move the legs. This is usually what people mean by “spina bifida.”
Meningocele A fluid-filled sac pushes through an opening in the back, but the spinal cord isn’t in it Little or no nerve damage; may cause minor disabilities
Spina bifida occulta A small gap in the bones of the spine, with no opening or sac The mildest type. Usually causes no disabilities and is often not found until later in childhood or adulthood, if ever

Hispanic women have the highest rate of having a baby with spina bifida in the U.S.: about 3.8 per 10,000 live births, compared with about 3.1 for non-Hispanic white women and 2.7 for non-Hispanic Black women.

Known risk factors

Research has identified several factors that raise the chance of having a baby with spina bifida. Having one doesn’t mean your baby will have it, and many babies with spina bifida are born to parents with none of them.

Not getting enough folic acid. This is the best-studied factor. The neural tube closes 21 to 28 days after conception, so what matters is your folate level in the weeks before and right after you conceive.

Certain medicines. Some anti-seizure medicines, such as valproic acid and carbamazepine, and other medicines that lower folate levels, such as methotrexate, are linked to higher risk, according to MedlinePlus. If you take any of these, talk with your doctor before trying to get pregnant. Don’t stop a seizure medicine on your own; uncontrolled seizures carry their own risks.

Diabetes that isn’t well controlled. High blood sugar in early pregnancy raises the risk, according to the CDC. Getting blood sugar in range before pregnancy helps.

Obesity. Obesity before pregnancy is linked to a higher risk, according to MedlinePlus.

Overheating or fever. A high body temperature early in pregnancy, from a fever or from heat sources like hot tubs and saunas, is linked to higher risk, according to the CDC. If you get a fever while trying to conceive or early in pregnancy, call your provider about how to bring it down safely.

Family history. If you’ve already had a pregnancy affected by a neural tube defect, or a close family member has one, your risk is higher than average. The CDC recommends 4,000 mcg of folic acid a day, under a doctor’s care, for women who’ve had an affected pregnancy.

What lowers the risk

You can’t control every factor, but several of the biggest ones can be addressed before pregnancy.

  1. Take 400 mcg of folic acid every day. The U.S. Preventive Services Task Force recommends 400 to 800 mcg a day for anyone planning or able to become pregnant, starting at least one month before conception and continuing through the first 2 to 3 months. Most prenatal vitamins contain it.
  2. Review your medicines with your doctor before trying to conceive, especially seizure medicines.
  3. Get diabetes under control before pregnancy, with your provider’s help.
  4. Avoid overheating in early pregnancy, and treat fevers promptly with your provider’s guidance.
  5. Ask about a higher folic acid dose if you’ve had a pregnancy affected by a neural tube defect.

How much difference folic acid makes. Since the U.S. began requiring folic acid in enriched grains in 1998, neural tube defect rates have fallen 28%. About 1,300 babies a year are born without a neural tube defect who otherwise would have had one, and spina bifida cases that do occur tend to be less severe, according to the CDC.

Folic acid lowers the risk; it doesn’t remove it. If your baby is diagnosed with spina bifida despite your best efforts, it isn’t because you did something wrong.

How it’s found during pregnancy

Spina bifida is often found before birth through routine prenatal tests, according to the CDC:

  • Blood test. An AFP (alpha-fetoprotein) test, sometimes part of a “quad screen,” can show a high AFP level, which may point to spina bifida. A screening result means more testing is needed; it isn’t a diagnosis.
  • Ultrasound. Spina bifida can often be seen on an ultrasound.

Sometimes it isn’t found until after birth, for example from a dimple or hairy patch of skin on the baby’s back, followed by imaging. Spina bifida occulta may not be found until adulthood, or ever.

Treatment before and after birth

For myelomeningocele, surgery to close the opening can happen during pregnancy or shortly after birth. A major study called the MOMS trial found that surgery before 26 weeks of pregnancy lowered the risk of death in infancy, reduced the need for a brain shunt in the first year, and improved movement in childhood. It also carries risks, including problems with the placenta and infection, so it’s a decision to make with a specialized team.

Life with spina bifida

Spina bifida affects people across their whole lives. At least 92,551 insured people in the U.S. were living with it in 2019, according to the CDC. With good medical care, the CDC says, people with spina bifida can reach their full potential. If you’ve received a diagnosis, the Spina Bifida Association connects families with clinics and support.

Related reading

Sources

This article is for general information and is not a substitute for advice from your health care provider.