Environmental Public Health Tracking: Anencephaly Data
A birth defect is a problem that happens while the baby is developing in the mother's body. Most birth defects happen during the first three months of pregnancy. A birth defect may affect how the body looks, works, or both.
Anencephaly is one type of birth defect. Review the FAQs below for more information about anencephaly.
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Anencephaly (pronounced an-en-sef-uh-lee) is a birth defect that affects the closing of a narrow channel, called the neural tube. Normally, the tube folds and closes during the third and fourth weeks of pregnancy to form the brain and spinal cord. Anencephaly prevents the neural tube that forms the brain from closing, which causes the baby to be born without the front part of the brain or a cerebrum (the thinking and coordinating part of the brain). Often, the brain tissue is exposed and not covered by bone or skin.
Researchers estimate that each year about 850 babies, or 1 in every 4,600 babies, in the United States will be born with anencephaly.*
*Mai CT, Isenburg JL, Canfield MA, Meyer RE, Correa A, Alverson CJ, Lupo PJ, Riehle‐Colarusso T, Cho SJ, Aggarwal D, Kirby RS. "National population‐based estimates for major birth defects, 2010–2014." Birth Defects Research. 2019; 111(18): 1420-1435.
Unfortunately, almost all babies born with anencephaly will die. Babies born with anencephaly are usually blind, deaf, unconscious, and unable to feel pain.
The cause of anencephaly is unknown. Scientists believe that many factors are involved.
The CDC is working with researchers to study risk factors that can increase the chance of having a baby with anencephaly. Researchers think folic acid may play a role in prevention of anencephaly. There was a 21% decline in babies born with anencephaly once the United States began fortifying grains with folic acid.
Currently, there is no known way to prevent anencephaly, although steps can be taken to lower the risk. Researchers think folic acid may play a role in prevention of anencephaly. There was a 21% decline in babies born with anencephaly once the United States began fortifying grains with folic acid.
CDC recommends that all women of childbearing age consume 400 micrograms of folic acid daily. Women can take steps before and during pregnancy to be healthy, including not smoking and not drinking alcohol during pregnancy. To learn more about preventing birth defects, visit the CDC’s page on birth