Neural Tube Defects: Types, Causes, and Prognosis

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If you are pregnant, have ever been pregnant, or have even talked to a doctor about considering a pregnancy, chances are you have been told to take folic acid before conception and in early pregnancy. The reason for this guideline is to reduce the risk of neural tube defects in the baby. But what exactly are neural tube defects, and how do they affect your pregnancy loss risk?

What Neural Tube Defects Mean

Neural tube defects are birth defects of varying severity that result from disruptions in the development of the neural tube, which is the early stage of development of the spinal cord and nervous system. The neural tube forms in very early pregnancy, right around the time you miss your first menstrual period.

Failure of the neural tube to close properly can result in neural tube defects of varying severity, with some neural tube defects being mild and barely noticeable while others are 100% fatal.

Neural tube defects can be open or closed, meaning that the defects may be uncovered or covered by skin. Spina bifida is the most common type of neural tube defect. It is estimated that there are approximately 166,000 people living with spina bifida in the United States.

While spina bifida generally does not result in miscarriage, it can cause severe physical disabilities that may not be correctable with surgery. Anencephaly is another common category of neural tube defects, in which the baby's brain does not develop fully or at all. Babies with anencephaly are often stillborn, and those who make it to delivery always die within a few days of birth.


Neural tube defects are diagnosed during pregnancy, usually via a combination of prenatal screening blood tests, ultrasound, and possibly, an amniocentesis. Neural tube defects may also be diagnosed at birth in women who did not receive prenatal testing.


Researchers do not know exactly what causes the neural tube to fail to close properly in babies with neural tube defects. Some people may have a higher risk because of genetic factors. But no specific gene is responsible for most neural tube defects, and the true cause may be environmental or even viral in origin.

The risk definitely seems to be lower in moms with adequate folic acid intake, and a large body of evidence shows that taking folic acid before conception can prevent as many as 70% of all cases of neural tube defects.

If you have had a baby with a neural tube defect in the past, there is an increased risk of neural tube defects in subsequent pregnancies. So it is important to talk to your doctor about what prevention methods and screening tests might make sense in your situation.


According to the Centers for Disease Control and Prevention, approximately 3,000 babies are born with neural tube defects in the United States each year. If you have recently learned that your baby has a neural tube defect, it is important that you talk to a knowledgeable pediatrician or another health care practitioner who can prepare you for what your baby's prognosis and needs are likely to be.

Although conditions like anencephaly have a lethal prognosis, other conditions such as spina bifida can be highly variable in severity among individuals. Regardless of the specifics of the condition, it is normal and expected to have feelings of grief and being overwhelmed about what lies ahead.

Know that your baby's condition is not your fault.

Even if you were not taking folic acid before conception, there is no way to know for certain that it would have changed the outcome for your baby. All you can really do in these cases is look forward and make plans for what lies ahead. Your doctor should be able to give you information on what to expect.

4 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Duke University, Duke Molecular Physiology Institute. Neural tube defects.

  2. Spina Bifida Association. Expectant parents: What is spina bifida?

  3. Centers for Disease Control and Prevention. Preventing neural tube birth defects.

  4. Centers for Disease Control and Prevention. Folic acid & neural tube defects: Data & statistics. Reviewed November 9, 2017.

By Krissi Danielsson
Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage.