What Causes Spina Bifida?

Although scientists are not sure why the neural tubes fail to develop or close correctly in some infants, they think that the explanation behind spina bifida may be genetic, nutritional or environmental – or a combination of these causes.

There does appear to be some definite risk factors that increase the chance of having a baby with spina bifida. For example, a family history of neural tube defect (NTD) clearly plays a role. The rates of spina bifida are significantly higher among couples in which at least one was born with a neural tube defect or has a close relative with one. Also, a previous pregnancy with a baby with a neural tube defect increases a woman’s risk of having another such pregnancy by approximately 20 times; that risk increases further if two previous children have been born with a NTD. Still, 95 percent of babies born with spina bifida have no family history of it.

Here are some of the other risk factors that increase the likelihood of spina bifida:

  • Diabetes in the mother: particularly when blood sugar levels are elevated in early pregnancy. Good blood sugar control and diabetes management may decrease the risk.
  • Medically diagnosed obesity in the mother: women who are obese before becoming pregnant are at a higher risk for having a baby with spina bifida than women of average weight. The link between pre-pregnancy obesity and neural tube birth defects is unclear, but one theory is that poor eating habits and inadequate nutrition may contribute. Another theory is that obese women frequently have diabetes – a known risk factor for spina bifida and other neural tube defects.
  • A history of seizure disorders in the mother and the use of certain anticonvulsants: medications such as valproic acid and carbamazapine may set the stage for NTDs because they block the body’s ability to process folic acid.
  • High body temperatures during early pregnancy: elevated core body temperature by even three or four degrees (such as from prolonged fevers or sauna and hot tub use) very early in pregnancy has been linked with increased risk of spina bifida.
  • Inadequate folic acid intake in the mother’s diet: folic acid (vitamin B-9) in the mother’s diet is key to the development of a healthy fetus. Lack of folic acid increases the risk of spina bifida and other neural tube defects. That is why vitamin supplements given to pregnant mothers typically contain folic acid. To help decrease the likelihood of spina bifida and other neural tube defects, the FDA mandated that all enriched cereal grain products be fortified with folic acid. (For more information on folic acid, see Can Spina Bifida Be Prevented?)
  • Lower socioeconomic status: again, poor nutrition may be the key issue here.

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Resources:

Spina Bifida Associaton
Who is at risk for Spina Bifida?

Mayo Clinic
Spina Bifida Causes
Spina Bifida Risk Factors