Anencephaly is a condition affecting the development of the brain and often the spinal cord. It occurs at birth and is a very serious condition. Sadly, babies are not able to survive anencephaly and the baby is either stillborn (born dead) or dies within a few hours to days of birth.

In this article

What are the symptoms?

Anencephaly is what is known as an open neural tube defect. It occurs when the upper part of the neural tube fails to close. This basically means that the skull and overlying scalp are absent and a severely abnormal brain structure is open to outside of the body. There are various sub-groups of anencephaly depending on the involvement of the neck and if it is associated with spina bifida, which is another type of neural tube defect.

Associated abnormalities include hydronephrosis (excessive enlargement of the fluid collecting system for the kidneys), cleft lip and/or palatediaphragmatic hernia, Exomphalos (see entry Abdominal Exstrophies) and horseshoe kidneys. In addition, spinal abnormalities and abnormal postures of the foot are also observed.

What are the causes of anencephaly?

In most cases the cause of anencephaly is unknown. It is possible that anencephaly may be associated with abnormal genes, but as yet no specific genetic anomaly has been recognised.

How is anencephaly diagnosed?

Anencephaly can be detected prenatally by ultrasound sometimes as early as 14 weeks depending on the how the developing baby (fetus) is positioned in the womb. It should be easily visible at 20 weeks on the ultrasound.

Amniocentesis and measurement of the levels of alpha feta protein in the amniotic fluid (fluid that surrounds the baby in the womb) can confirm the diagnosis. Alpha feta protein would be expected to be extremely high if the condition is present.

Receiving a diagnosis is very distressing. Some parents may choose not to continue with the pregnancy if the condition is discovered before birth. Antenatal Results and Choices (ARC) can offer support at this time (see entry Fetal Abnormality).

Can you treat anencephaly?

Sadly anencephaly cannot be treated. The levels of the condition are dropping in the Western world as more women are taking folic acid in the early stages of pregnancy, which helps to prevent neural tube defect in a developing baby.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
The risk of a further pregnancy with anencephaly and spina bifida is said to be 1 in 50 if there has been one previously affected pregnancy and 1 in 5 if there have been two previously affected pregnancies.

Prenatal diagnosis
Anencephaly can be detected prenatally by ultrasound. Amniocentesis and measurement of the levels of alpha feta protein in the amniotic fluid can confirm the diagnosis.

Support for parents and families

Information and support in the UK for anencephaly is provided by the Spina Bifida Hydrocephalus Information Networking Equality – SHINE (see entry Spina Bifida).


Medical text written February 2006 by Mr N Buxton. Last updated February 2013 by Mr N Buxton, Consultant Paediatric Surgeon, Alder Hey Children’s Hospital, Liverpool, UK.

Although great care has been taken in the compilation and preparation of all entries to ensure accuracy, we cannot accept responsibility for any errors or omissions. Any medical information is provided is for education/information purposes and is not designed to replace medical advice by a qualified medical professional.

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