Alternative Names

Aprosencephaly with open cranium

Definition of Anencephaly

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

Causes, incidence, and risk factors

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.

Signs 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.


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

Expectations (prognosis)

This condition usually causes death within a few days.


Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 5/12/2009

Ultrasound, normal fetus - ventricles of brain

ADAM Medical Encyclopedia

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