Anencephaly

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Ultrasound, normal fetus - ventricles of brain

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

Aprosencephaly with open cranium

Anencephaly is a neural tube defect that occurs early in the development of an unborn baby. Neural tube defects involve the tissue that grows into the brain and spinal cord. Anencephaly results when the upper portion of the neural tube fails to close. Why this happens is not known. Possible causes include environmental toxins and low intake of folic acid during pregnancy.

Anencephaly occurs in about 4 out of 10,000 births. The exact number is unknown, because many of these pregnancies spontaneously abort. Having one anencephalic infant increases the risk of having another child with neural tube defects.

Review Date: 08/23/2005
Reviewed By: John Goldenring, MD, MPH, Department of Pediatrics, Children's Hospital, San Diego, CA. Review provided by VeriMed Healthcare Network.