What is anencephaly?
Anencephaly is a severe congenital (present at birth) condition that occurs when a fetus’s brain, skull and scalp don’t develop properly. Parts of the brain and skull are missing, leaving the brain tissue that forms exposed and unprotected.
Congenital conditions like anencephaly that affect the brain, spinal cord and nerves are called neural tube defects (NTDs). The neural tube is tissue in a fetus that becomes the brain, spinal cord and spine. An NTD occurs if the tube doesn’t close properly when it forms during the first month of pregnancy. Anencephaly occurs when the top part of the neural tube doesn’t close completely.
Other abnormalities of the fetal skull include:
- Meroacrania: In this milder form, a smaller area of the skull is missing.
- Acrania: The entire skull is missing, and the brain is not fully formed.
- Holoanencephaly: This is the most severe type, in which the brain is completely missing.
Babies who have anencephaly have a higher chance of being born prematurely or being stillborn. Unfortunately, most full-term babies who have anencephaly pass away within a few hours or days after birth.
What causes anencephaly?
The causes of anencephaly aren’t fully understood, but researchers believe that a combination of genetic and environmental factors may be involved. Most cases of anencephaly occur in families with no history of the condition, so it doesn’t appear to be an inherited condition.
Certain factors may increase a mother’s risk of having a baby with anencephaly. Not everyone with risk factors will have a baby with anencephaly, and some women without risk factors can have a baby with the condition.
The risk factors for anencephaly include:
- Folic acid (vitamin B9) deficiency before and during pregnancy
- High heat exposure during pregnancy, such as having a fever or using a hot tub or sauna
- Certain medications that treat seizures, migraine headaches and bipolar disorder
- Opioid use during pregnancy
- Uncontrolled diabetes before pregnancy
Taking a 400-microgram (4 milligrams) supplement of folic acid every day, before and during pregnancy, can greatly reduce the risk of having a baby with anencephaly.
Who gets anencephaly?
Anencephaly makes up about half of all cases of neural tube defects. According to the Centers for Disease Control and Prevention, about one in 4,600 babies is born with anencephaly each year in the United States.
Female babies are three times more likely to develop anencephaly than male babies. Hispanic women are more likely than other ethnicities to have a baby with anencephaly.
What are the signs and symptoms of anencephaly?
Signs of anencephaly that can appear in a routine pregnancy ultrasound include:
- No skull bones on the back of the head
- Missing skull bones around the front and sides of the head
- Large areas of brain missing
- Folded ears
- Opening in the roof of the mouth (cleft palate)
- Congenital heart diseases (structural problems with the heart’s chambers, valves or walls)
- Buildup of amniotic fluid (the fluid that surrounds and protects your baby in your uterus), called polyhydramnios
What tests are used to diagnose anencephaly?
Our fetal care specialists can diagnose anencephaly during pregnancy or at birth, with a physical exam. The tests we use to diagnose anencephaly during pregnancy include:
- Alpha-fetoprotein (AFP) screening: Your doctor takes a sample of the mother’s blood to test for signs of NTDs and other conditions. AFP is a protein produced by the fetus, and a high level in the mother’s blood can be a sign of an NTD such as anencephaly.
- Fetal ultrasound: We perform a targeted, detailed ultrasound to closely examine your baby inside the uterus for signs of anencephaly.
- Amniocentesis: Your doctor inserts a needle through your abdomen into your uterus to take a small sample of amniotic fluid for testing. This test detects signs of NTDs, chromosomal disorders and other congenital conditions.
How is anencephaly treated?
Unfortunately, no treatment exists for anencephaly. Without proper brain and skull development, babies pass away either during pregnancy (miscarriage or stillbirth) or within the first few days of life. During pregnancy, our fetal experts will discuss all your options so you’re fully informed and comfortable with your path forward.
You may deliver vaginally unless you need a cesarean delivery for other health reasons. Some babies with anencephaly are in a breech position, which might require a cesarean.
After birth, we provide comfort care for you and your baby to relieve pain and other symptoms through our Neonatal Palliative Care Program. We also offer prenatal counseling and ongoing mental health support for parents and families.
Why choose us for management of anencephaly?
Finding out that your baby has anencephaly can be overwhelming. Our specialists at the Colorado Fetal Care Center have experience making this diagnosis and helping families navigate neural tube defects such as anencephaly. Our neonatal and palliative care experts give you the understanding, expertise and resources to help your family through this troubling diagnosis.
- Centers for Disease Control and Prevention: Facts about Anencephaly
- National Institutes of Health, Genetic and Rare Diseases Information Center: Anencephaly
- National Institutes of Health, U.S. National Library of Medicine: Anencephaly
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