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Genetic and Rare Diseases Information Center (GARD)

Other Names for this Disease
  • Absence of a large part of the brain and the skull
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What causes anencephaly?

The cause of anencephaly is not fully understood. Like other forms of neural tube defects (NTDs),this condition is likely caused by the interaction of multiple genes and environmental factors. Some of these factors have been identified, but many remain unknown.[1][2][3]

Changes in dozens of genes may influence the risk of anencephaly. The best-studied of these genes is MTHFR, which provides instructions for making a protein that is involved in processing the B-vitamin folate (also called folic acid or vitamin B9). Changes in other genes related to folate processing and genes involved in the development of the neural tube have also been studied as potential risk factors for anencephaly. However, none of these genes appear to play a major role in causing the condition.[1]

Researchers have also examined environmental factors that could contribute to the risk of anencephaly. A shortage (deficiency) of folate appears to play a significant role. Studies have shown that women who take supplements containing folic acid before they get pregnant and very early in their pregnancy are significantly less likely to have a baby with anencephaly or a related neural tube defect. Other possible risk factors for anencephaly include diabetes mellitus, obesity, exposure to high heat (such as a fever or use of a hot tub or sauna) in early pregnancy, and the use of certain anti-seizure medications during pregnancy. However, it is unclear how these factors may influence the risk of anencephaly.[1]
Last updated: 11/28/2011

  1. Anencephaly. Genetics Home Reference. February 2011; Accessed 11/28/2011.
  2. NINDS Anencephaly Information Page. National Institute of Neurological Disorders and Stroke (NINDS). 2010; Accessed 11/28/2011.
  3. Best RG, Gregg AR, Lorenzo N. Anencephaly. eMedicine. 2010; Accessed 11/28/2011.