Anencephaly is a fatal birth defect. It occurs when the fetal brain and skull don’t develop in your uterus as expected. Babies born with the condition die within a few hours or days. Most pregnancies end in miscarriage. You can lower your risk by taking the recommended dose of folic acid before and during pregnancy.
This condition affects a baby’s nervous system, which includes their brain, spine and nerves. It happens when the neural tube (which is responsible for growing the brain, skull, backbones and spinal cord) doesn’t develop or fails to close as it should in the first month of pregnancy. That’s why anencephaly is a type of cephalic disorder called a neural tube defect.
The brain is essential to survival. It controls body functions, emotions and memory. Since anencephaly affects how the brain develops, babies born with anencephaly usually live only a few minutes, hours or days. Most pregnancies with anencephaly end in miscarriage or stillbirth.
There are three types of anencephaly and all three are fatal for the fetus:
Anencephaly is a common type of neural tube defect. Studies estimate it happens in 1 in 1,000 pregnancies. But since most anencephaly pregnancies end in miscarriage, the condition only affects an estimated 1 in 10,000 newborns in the United States.
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Signs of anencephaly include:
A healthcare provider will offer tests to detect conditions like anencephaly during pregnancy.
The birthing parent may not be aware of any symptoms until a blood test or an ultrasound.
Newborns with anencephaly don’t have:
Not all newborns with anencephaly develop a brainstem. If they do, they may have reflexes and automatically respond to touch. Seeing your newborn respond like this might give you hope. But this isn’t a sign that they’re aware of your touch or that they’ll be able to live long-term with this condition.
A problem with how the neural tube forms and closes causes anencephaly. The neural tube is a flat piece of tissue that grows into a tube shape. Each part of the neural tube helps parts of a baby’s body grow:
Anencephaly happens when the top part of the neural tube doesn’t close during embryonic development. This occurs during the third and fourth week of pregnancy. The fetus continues to form, except the front of the brain (forebrain) and the top of the brain (cerebrum) don’t grow. Other parts of the brain may develop as expected but no skin or skull cover them.
As far as we know, anencephaly isn’t inherited (passed down in families). In most cases, it occurs without any family history of the condition (sporadic genetic mutation). But if you had a child with a neural tube defect (NTD) before, like spina bifida, you have a higher chance of having a baby with anencephaly. This risk is about 2% to 3 %, which is 20 times higher than in someone who hasn’t had a previous baby with spinal bifida.
Certain medications and risk factors increase the chance of having a baby with anencephaly or another neural tube defect (NTD) including:
When you’re pregnant, you’ll have certain prenatal screening tests that can detect birth defects and other conditions that might affect the health of the fetus. Prenatal tests that can diagnose anencephaly include:
A healthcare provider may diagnose anencephaly after a baby is born if you opt out of prenatal screening tests, including ultrasounds. This happens during your newborn’s physical exam.
A healthcare provider may be able to detect anencephaly after eight to 12 weeks in the first trimester. On average, screenings for anencephaly usually happen around 18 to 20 weeks.
There’s no available cure or treatment for anencephaly. Almost all babies born with anencephaly die within a few hours or days after birth. Your newborn’s healthcare providers will support you and help you grieve and say goodbye.
Although it isn’t always possible to prevent anencephaly, you may be able to reduce your chance of having a child with the condition by:
Anencephaly is a fatal condition with a very poor outlook. Most fetuses with anencephaly pass away before birth, and the pregnancy ends in miscarriage. Almost all babies born with anencephaly die within a few minutes, hours or days.
You may worry that your newborn is distressed, uncomfortable or in pain, but babies with anencephaly can’t feel pain. Infants who survive birth may seem to respond to touch or sound. But they aren’t really responding to feeling or sound because they don’t have the largest part of their brain (cerebrum), which allows them to move, think, feel and respond.
Learning that your baby has anencephaly is extremely difficult. Your care team will help you and your loved ones say goodbye and provide follow-up care to make sure you and your family are doing as well as you possibly can after the loss of a child.
You may find that you need support or someone to talk to. If so, your healthcare team can connect you to a mental health professional or a bereavement support group where you can share your feelings with others who’ve had similar losses. It’s understandable if you feel heartbroken and hopeless, but surrounding yourself with a network of support can help you with any grief you’re feeling.
If you’re planning to become pregnant, start with a preconception counseling visit. A healthcare provider can help you maintain good health to lower your risk of having a child with a birth defect.
If you’re having any symptoms of a miscarriage, like heavy bleeding, cramps and/or severe back or abdominal pain, contact your pregnancy care provider right away.
A note from Cleveland Clinic
Severe birth defects are still possible even if you’ve done everything your healthcare provider recommends to have a healthy pregnancy. Anencephaly is an extremely devastating diagnosis to hear. Your healthcare team will be beside you to answer all your questions and help you come to terms with the loss. It may help to find comfort in talking with a mental health professional, joining a support group or surrounding yourself with a close network of friends and family.
Last reviewed by a Cleveland Clinic medical professional on 08/29/2023.
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