Anencephaly: What does it mean?

Julia Wise

Finding out that a baby has a congenital abnormality can be a life-changing experience for parents. The most common of these abnormalities is called anencephaly. Babies with anencephaly do not develop parts of the skull and brain needed to support life. Anencephaly is present in approximately 3 in 10,000 pregnancies (1). 

While there have been some rare cases of babies with anencephaly living past a year, most do not live past 24 hours following birth (2). According to patient reports, a quarter of babies with anencephaly died before birth, but this data hasn’t been independently verified (3). The sections of the brain and skull that do not develop in anencephaly are important for controlling bodily functions and survival. These parts of the brain also control pain and feeling, so babies born with anencephaly may move but are not responding to a sense of pain or discomfort. 

Low levels of folate early in a pregnancy can increase the risk of anencephaly, so taking prenatal vitamins that have folate at the first sign of a pregnancy is one of the easiest forms of prevention (4). There are other risk factors, like genetics and exposure to chemical agents or diseases, but a majority of anencephaly cases are linked to folate deficiencies. 

Anencephaly can be detected before birth using a common blood test known as a quad screen (5). A quad screen measures levels of AFP (alpha-fetoprotein), HCG (human chorionic gonadotropin), estriol (a form of estrogen), and inhibin-A. Because the brain has not been closed off in anencephaly, a higher than expected level of AFP will appear on the quad screen. More testing may be recommended following an abnormal quad screen, such as an ultrasound or chorionic villus sampling (6). 

This image shows the results of an ultrasound of a fetus with anencephaly at 28 weeks. The face can be seen on the right side of the image, with two prominent eye sockets. The area above the eyes is empty. This is where the brain and skull would be in a healthy fetus. 

As anencephaly is a fatal diagnosis, parents of a child with anencephaly may benefit from a support group and therapy. Severe birth defects such as anencephaly may occur even after following all recommendations for a healthy pregnancy, and feelings of guilt and sadness are normal. Healthcare providers can play a valuable role in supporting parents through a difficult diagnosis, and may offer a different prognosis as medicine continues to evolve and grow (6). 

Anencephaly remains one of the most severe birth defects worldwide and is an extremely devastating diagnosis to receive. Providing compassionate care and support remains one of the best ways to allow parents to understand and make sense of their diagnosis. 

References 

1. Monteagudo A. Exencephaly-anencephaly sequence. American Journal of Obstetrics and Gynecology. 2020 Dec;223(6). doi:10.1016/j.ajog.2020.08.176 

2. Dickman H, Fletke K, Redfern RE. Prolonged unassisted survival in an infant with anencephaly. BMJ Case Reports. 2016 Oct 31;2016. doi:10.1136/bcr-2016-215986 

3. Report about the birth and life of babies with anencephaly [Internet]. [cited 2026 Apr 10]. Available from: https://www.anencephaly.info/e/report.php 

4. Anencephaly [Internet]. Centers for Disease Control and Prevention; [cited 2026 Apr 10]. Available from: https://www.cdc.gov/birth-defects/about/anencephaly.html 

5. professional CC medical. Quad Marker Screen: Purpose, procedure & results [Internet]. 2026 [cited 2026 Apr 10]. Available from: https://my.clevelandclinic.org/health/diagnostics/4698-pregnancy-quad-marker-screen 

6. What is anencephaly? [Internet]. 2025 [cited 2026 Apr 10]. Available from: https://my.clevelandclinic.org/health/diseases/15032-anencephaly 

7. Dilmen N. Ultrasound Scan ND 158 [Internet]. Wikipedia. 1997 [cited 2026]. Available from: https://commons.wikimedia.org/wiki/File:Ultrasound_Scan_ND_158.jpg