Question of the Month: Is there a genetic blood test yet that predicts a neural tube defect?

Currently the screening test for neural tube defects that is available to pregnant women remains a serum alpha-fetoprotein blood sample drawn from the mother at 15-20 weeks gestation. If the results of this test are elevated, then a fetal ultrasound is recommended to look for sonographic features of a neural tube defect. Depending on the results, an amniocentesis may also be recommended.

Using this screening method, there is a 75-90% chance that an open neural tube defect will be detected if present. On open neural tube defect means that the neural sac is open to the outside of the fetus. If the sac is closed, the alpha-fetoprotein will likely not be elevated, but the fetal ultrasound may still see the spinal defect.

While there have been many different genetic findings in studies of individuals with Spina Bifida and their mothers, there is not a gene test that currently predicts a future pregnancy affected with a neural tube defect.

The MTHFR gene has been studied due to its association with folic acid metabolism. There is a certain genetic variant of this gene that is found more often in mothers with a child born with a neural tube defect, but the predictability of this variant is not sufficient to be used as a test.

As always, folic acid supplementation is believed to lower the risk of neural tube defects, even if the mother has the affiliated MTHFR variant. All women should take at least 400mcg of folic acid daily starting at least 1-3 months before pregnancy and well into the first trimester. Women who have family with neural tube defects should take 4mg of folic acid.

The SBA Fact Sheet, Genetics and Spina Bifida provides a good overview of the genetic and environmental factors that may cause a baby to be born with Spina Bifida.

For more information on tethered cord, please visit the Spina Bifida Association fact sheet.

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