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Updated June 20, 2014

Neural tube defects are conditions in which the developing neural tube does not close properly during the baby's development very early in the first trimester. Neural tube defects have a wide range of severity, from only minor health concerns to being 100% fatal. On the severe range of that spectrum is anencephaly, one of the most devastating diagnoses expectant parents can receive during pregnancy.

What Anencephaly Means:

In anencephaly, crucial parts of the baby's brain and skull fail to form. Without these brain areas, the baby can never gain consciousness or carry out the physical functions of life. Because the skull is also affected by the disorder, a baby with anencephaly is usually physically deformed and parts of the brain may be exposed. Babies affected by anencephaly frequently are stillborn or die at birth. Even if born alive, babies with anenecephaly always die within a few days of birth. There is no treatment that can change the prognosis.


Anencephaly is often apparent on the ultrasound by the second trimester, but the first clue might be abnormalities in the alphafetoprotein blood test. Amniocentesis may be used in the diagnosis as well. An anencephaly diagnosis is unlikely to be a false positive.


Anencephaly is not believed to have a strictly genetic origin but appears to be the result of a combination of genetic and environmental factors. The interplay of these factors disrupts the closure of the neural tube, which occurs between the third and fourth week of pregnancy. The specifics of the factors at work in anencephaly and other neural tube defects are still not well understood.

Risk Factors:

There is evidence that having an adequate intake of folic acid before conception will reduce the risk of having a baby affected by any neural tube defect, although the reasons for this are not well understood. The reduced risk of neural tube defects is why doctors advise all women of childbearing ages to take folic acid supplements or eat folic acid-rich foods on a regular basis (don't wait until you're already pregnant). Yet anencephaly can occur even when moms eat a perfect diet, so it cannot necessarily be prevented and it is definitely not anyone's fault when it does occur.

Risk of Recurrence:

Parents who have a child with anencephaly may have a 4 to 10% risk of having a child affected by neural tube defects in a future pregnancy, although the specific neural tube defect might not be anencephaly. Doctors may advise taking high doses of folic acid before conceiving again and may recommend that the couple work with a genetic counselor as well.

Deciding What to Do After the Diagnosis:

The decision of what to do can be heart wrenching. Many parents decide to terminate the pregnancy after receiving a diagnosis of anencephaly, knowing that there is zero chance that the baby will live. Ending the pregnancy can help parents to move forward and begin the grieving process.

Other parents may have strict religious or other personal beliefs against abortion, and they may choose to carry the pregnancy to term anyway even with the full knowledge that the baby will not live more than a few days at most.

If you are facing this tragic choice, be sure to take your time and do what feels right for you and your partner. Give yourself room to grieve the loss of the baby. It is OK to be angry, to be sad, or to feel anything else that you might feel. Your hospital may have grief counselors available, and there are numerous support groups available on the Internet that target couples dealing with an anencephaly diagnosis (although many are slanted in favor of a specific course of action for dealing with the pregnancy).


Anencephaly. Neurological Disorders. University of Virginia Health System. Accessed: February 21, 2008. http://www.healthsystem.virginia.edu/uvahealth/peds_neuro/anenceph.cfm

NINDS Anencephaly Information Page. National Institute of Neurological Disorders and Stroke. Accessed: Feb. 20, 2008. http://www.ninds.nih.gov/disorders/anencephaly/anencephaly.htm

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