Neural Tube Defects (e.g. Spina Bifida and Anencephaly)

Neural Tube Defects (e.g. spina bifida and anencephaly)

If you have just found out through prenatal testing that your baby has a neural tube defect or may have a neural tube defect and are looking for more information, the Genetic Support Foundation is a good starting point.

There are other important resources out there, including your doctor and genetic counselor. We have also compiled a list of resources that can provide you with additional information and support.

After reviewing the information below, if you have a question that you are having difficulty finding an answer for, please feel free to contact us.

Overview of Neural Tube Defects

Neural tube defects (NTDs) are birth defects involving the brain and spinal cord. They happen in about 1-2 per 1000 pregnancies in the United States.  There are different types of neural tube defects with different levels of severity; two of the most common types are called spina bifida and anencephaly (more severe). To reduce the risk for neural tube defects, it is recommended that women take 400 mcg of folic acid prior to becoming pregnant and through the early part of the pregnancy.  Most cases of neural tube defects are detected during a level II ultrasound in the second trimester of the pregnancy. Depending on the type of neural tube defect, surgery is typically performed after the baby is born (or possibly during the pregnancy) but this does not reverse the nerve damage that has already occurred.



How do neural tube defects happen?

Very early in the development of the baby (within the first month of pregnancy), certain cells form a tube (called the neural tube) that later become the spinal cord, the brain, and the nearby structures that protect them, including the backbone (also called the spinal column or vertebrae). Ultimately, the top of the tube becomes the brain and the remainder becomes the spinal cord. The neural tube actually starts out flat in shape/structure and as development progresses it folds on itself to form a tube.  This tube has to seal up to form the “tube” structure.  A neural tube defect occurs when somewhere along the tube it does not seal up, resulting in a hole in the spinal column or another type of defect.  NTDs can cause serious problems for babies, including death.  There are different types of NTDs and the severity often depends on where along the tube the opening resides.



Is there anything I can do to prevent neural tube defects?

If women of childbearing age take 400 micrograms of folic acid every day before (starting at a month before) and during early pregnancy, it may help reduce their baby’s risk for NTDs. Folic acid is a B vitamin that every cell in your body needs for normal growth and development.



If I already have a child with a neural tube defect, is there an increased chance my other children will get it too?

Neural tube defects (NTDs) are often sporadic, meaning we don’t see anyone else in the family with this condition.  However, NTDs can cluster or run in some families.  NTDs are what we call a multifactorial disorder.  Multifactorial disorders are caused by both genetic and environmental factors; the genetic factors typically involve multiple genes or instructions.  So, if you have a child or another family member(s) who was born with a neural tube defect, your chances of other children being born with a NTD are slightly increased above the general population background risk.



Types of Neural Tube Defects

Although there are others, a couple of the more common types of NTDs are spina bifida and anencephaly.

What is spina bifida?

Spina bifida is the most common type of NTD, affecting approximately 1 in 2000 to 1 in 4000 babies born in the United States.   In this condition, the vertebrae do not close completely, and a part of the spinal cord pokes through the spine and skin.  Since the spinal cord is not protected, damage can occur and this is what causes may of the symptoms seen in spina bifida.  The symptoms are often related to how far up or down on the spine the opening occurs.  For openings very low, the main symptoms may be bladder and bowel control issues.  If the opening is further up on the spine, this may result in inability to walk or paralyzed legs. There also are milder forms of spina bifida that cause fewer problems for children.

Spina bifida is treated with surgery before or after birth, however, often the damage has already been done to the nerves involved prior to surgery; surgery does not typically take away the problems associated with spina bifida.

For more information about spina bifida, see the side bar or click HERE.

What is anencephaly?

Anencephaly is one of the most severe forms of  NTDs and affects approximately 1 in 4,859 (1) babies born.  Anencephaly occurs when the upper part of the neural tube that forms the brain does not close completely.  Most babies with anencephaly are stillborn or pass away shortly after birth. For more information about anencephaly click HERE.

 

1. Parker SE, Mai CT, Canfield MA, Rickard R, Wang Y, Meyer RE, et al; for the National Birth Defects Prevention Network. Updated national birth prevalence estimates for selected birth defects in the United States, 2004-2006. Birth Defects Res A Clin Mol Teratol. 2010;88(12):1008-16.




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