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A.D.A.M. Medical Encyclopedia [Internet]. Atlanta (GA): A.D.A.M.; 2013.

A.D.A.M. Medical Encyclopedia.

Anencephaly

Aprosencephaly with open cranium

Last reviewed: May 10, 2013.

Anencephaly is the absence of a large part of the brain and the skull.

Causes

Anencephaly is one of the most common neural tube defects. Neural tube defects are birth defects that affect the tissue that grows into the spinal cord and brain.

Anencephaly occurs early in the development of an unborn baby. It results when the upper part of the neural tube fails to close. Why this happens is not known. Possible causes include environmental toxins and low intake of folic acid by the mother during pregnancy.

Anencephaly occurs in about 1 out of 10,000 births. The exact number is unknown, because many of these pregnancies result in miscarriage. Having one infant with this condition increases the risk of having another child with neural tube defects.

Symptoms

  • Absence of the skull
  • Absence of the brain (cerebral hemispheres and cerebellum)
  • Facial feature abnormalities
  • Heart defects

Exams and Tests

A pregnancy ultrasound is done to confirm the diagnosis. The ultrasound may reveal too much fluid is in the uterus. This condition is called polyhydramnios.

Other tests that may be done on the pregnant mother:

A pre-pregnancy serum folic acid test may also be done.

Treatment

There is no current therapy. Talk to your doctor about care decisions.

Outlook (Prognosis)

This condition usually causes death within a few days.

When to Contact a Medical Professional

A health care provider usually detects this condition during routine prenatal testing and ultrasound. Otherwise, it is recognized at birth.

If anencephaly is detected before birth, further counseling will be needed.

Prevention

It is important for women who may become pregnant to get enough folic acid.

There is good evidence that folic acid can help reduce the risk of certain birth defects, including anencephaly. Women who are pregnant or planning to become pregnant should take a multivitamin with folic acid every day. Many foods are now fortified with folic acid to help prevent these kinds of birth defects.

Getting enough folic acid can reduce the chance of neural tube defects by 50 percent.

For specific recommendations, see folic acid (folate).

References

  1. Kinsman SL, Johnston MV. Congenital anomalies of the central nervous system. In: Kliegman, RM, Behrman RE, St. Geme JW III, Schor NF, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 585.

Review Date: 5/10/2013.

Reviewed by: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.

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The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only — they do not constitute endorsementscof those other sites. © 1997–2011 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Copyright © 2013, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only — they do not constitute endorsementscof those other sites. © 1997–2011 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Copyright © 2013, A.D.A.M., Inc.

What works?

  • Preconception care for diabetic women to improve maternal and infant healthPreconception care for diabetic women to improve maternal and infant health
    Current guidelines in many countries including Australia, the United Kingdom and United States recommend preconception care of diabetic women. Pregnant women with type I or type II diabetes are at a greater risk of adverse outcomes in pregnancy such as high blood pressure (gestational hypertension) and preterm births. Pregnancy can also accelerate the development of diabetic complications (retinopathy, nephropathy, neuropathy, ischaemic heart disease, cerebrovascular disease, peripheral vascular disease). Babies born to mothers with type I or type II diabetes diagnosed before pregnancy may be larger and are at greater risk of infant death and congenital abnormality (such as neural tube defects including anencephaly and spina bifida). These infants are also at risk of developing type II diabetes in the long term. Because of the strong association between good control of a woman’s blood sugars (glycaemic control), as measured by haemoglobin A1c, and reduced congenital anomalies, glycaemic targets are central to preconception care.
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Figures

  • Ultrasound, normal fetus - ventricles of brain.

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