Spina Bifida Family Support
"Families Helping Families"
Provided by the Center for Human Genetics (CHG) at Duke University Medical Center
FACTS ABOUT NEURAL TUBE DEFECTS
A neural tube defect (NTD) is a birth defect caused by an opening in the spinal cord or brain. The early neural tube (future brain and spinal cord) begins as a flat area of skin. The neural tissue then rolls up to form the tube. Failure of the neural tissue to form a tube is a neural tube defect.
NTD's form very early-approximately 28 days after conception; often before a women even knows she is pregnant.
There many NTD's. They can be open (not covered by skin) or closed (covered by skin). The most common form of an open NTD is spina bifida, or myeleomeningocele, which is an opening in the spine. Anencephaly is another common open NTD and it results from a problem in how the brain and skull develop. A common form of closed NTD is lipomyelomeningocele, which is similar to myelomeningocele except that the skin covers this NTD, and fatty tissue is also involved.
NTD's are found in individuals of all ethnic backgrounds all over the world. Approximately 1 in 1,000 births in the U.S. is an individuals with an NTD.
Only 5% of all individuals who have an NTD have a relative who also has an NTD. However, the limited information we have at this time suggests that this condition is passed, or inherited, through the family. The inherited component may be a susceptibility to NTD's rather than a direct cause of NTD's.
The specific causes of NTD's are unknown, but it is believed that both genetic and environmental factors are involved.
Some forms of NTD's can be detected before the baby is born. Other forms are not detected until after birth or in childhood or even adulthood. Please contact a genetic counselor to discuss prenatal tests you or other relatives may consider to determine if a baby has an NTD.
There are no known genes identified as causing NTD's. Therefore, there is no genetic (DNA) test available that an individual can have to determine his or her chance of having a child with an NED. Our research may eventually lead to such a genetic test.
Known environmental factors with NTD development include maternal use of certain anti-seizure medications and maternal insulin-dependant diabetes during pregnancy.
Another known environmental factor is folic acid. Studies have shown that women who take folic acid prior to getting pregnant and through the first trimester reduce the chance of having a child with an NTD by 50%-70%. Folic acid does not prevent all cases of NTD's. And, despite taking folic acid in the recommended dose during the recommended time period, it is still possible to have a child with an NTD. It is not yet understood how folic acid works to decrease the chance of having a child with an NTD.
Prevention of NTD's by preconceptional folic acid supplementation has not bee studied in people other than women who have had a previous pregnancy or child with NTD. Therefore, there are no specific recommendations for taking high doses of folic acid for women who have had an NTD themselves, for other relatives, such as sisters, aunts, cousins, of someone with an NTD, or for the female partners of men who have an NTD.
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