You might already be aware of the term neural tube defects (NTD), or have heard it mentioned during your early prenatal appointments. Your care provider might have already discussed the importance of getting enough folic acid during pregnancy, to reduce the chances of neural tube defects, such as spina bifida (where the spinal cord does not develop properly in the womb).
Birth defects are structural changes that are present at birth. They can affect any organ or part of the body, and can range from mild to severe.
What is anencephaly?
Anencephaly is a serious birth defect that affects the fetal nervous system; it is therefore referred to as a neural tube defect. As a result of anencephaly, the brain and skull do not develop normally during pregnancy.
Babies affected by anencephaly are missing large parts of the brain and skull. The parts of the baby’s brain that remain are often exposed and not covered by bone or skin, and therefore are destroyed.
When does anencephaly occur?
Anencephaly is a type of neural tube defect that occurs early in pregnancy, usually in the third or fourth week, as the neural tube forms.
During early embryonic development, the neural tissue, which will eventually develop into the brain and spinal cord, starts off as a line of flat cells which then become a tube-like formation.
Anencephaly occurs when part of the neural tube fails to close properly. Abnormal neural tube closure affects normal brain development. This is sometimes referred to as an open neural tube defect.
How common is anencephaly?
Although anencephaly is one of the most common birth defects involving the fetal nervous system, the condition is still relatively rare.
It’s estimated that anencephaly occurs in around 1 in every 5,000-10,000 pregnancies; it is more common in girls than boys.
It’s difficult to assess numbers accurately, however, as the majority of pregnancies affected by anencephaly result in miscarriage in early pregnancy.
If you’re concerned about the possibility of miscarriage, read our article What Does Miscarriage Bleeding Look Like?
What causes anencephaly?
The cause of neural tube defects, such as anencephaly and spina bifida, is often unknown. They are likely to occur due to a combination of genetic and environmental factors.
Anencephaly is not thought to be passed down through families, and the majority of cases occur without any family history of the condition.
Who is at risk of anencephaly?
Research into birth defects suggests that having a prior pregnancy with a neural tube defect is by far the biggest risk factor for it to happen again; the type of defect, however, might be different.
If you’ve had a previous pregnancy with anencephaly, you have a 1 in 50 chance of it happening again in subsequent pregnancies.
If you’ve had a previous pregnancy affected by any neural tube defect, you have a 1 in 25 chance of your baby developing some type of neural tube defect in a future pregnancy.
Additional risk factors for anencephaly
Pregnant women who’ve already had a pregnancy affected by a neural tube defect, are at greater risk of it happening again, but there are some additional potential risk factors which might also increase the chances:
- Lack of folic acid (vitamin B9)
- Uncontrolled maternal diabetes
- High temperature, due to maternal fever or the use of saunas/hot tubs
- Medications – particularly anti-seizure, migraine, or bi-polar medications can affect the developing fetus
- Opioid use. Certain prescription medications and illegal opium drugs can affect fetal development
- Obesity.
To learn more about how weight can affect pregnancy, read our article, Excess Pregnancy Weight Increases Risk of Birth Defects, Study Finds.
How is anencephaly diagnosed?
Anencephaly is normally diagnosed during pregnancy or immediately after birth.
During pregnancy, it can be picked up in one of two ways:
- Prenatal tests
- Prenatal ultrasound
Prenatal tests
Anencephaly would result in abnormal results of prenatal screening, usually done during the first trimester. Genetic screening identifies those with a higher chance of certain genetic disorders or neural tube defects.
Screening tests involve a maternal blood test, which looks at the levels of maternal serum alpha fetoprotein (AFP). The baby’s liver makes AFP during pregnancy. High levels of this protein will be detectable in the mother’s blood if anencephaly is present.
Screening tests will not tell you definitively whether or not your baby has the condition. A ‘high chance’ screening result doesn’t necessarily mean your baby has one of those conditions.
You’ll be offered further diagnostic tests, such as an amniocentesis or Chorionic Villus Sampling (CVS) to confirm a diagnosis.
An amniocentesis involves taking a sample of amniotic fluid, by passing a thin needle through the amniotic sac, which will then be tested for markers of abnormal development.
To find out more, read our article Amniocentesis | Definition, Risks And What To Expect.
Anencephaly in ultrasound
Anencephaly can be diagnosed during a first trimester ultrasound. The use of ultrasound to diagnose anencephaly is very accurate.
A measurement from the top of your baby’s head to the baby’s bottom will be taken during the scan. This is known as the crown-rump length measurement or CRL. In a baby with anencephaly, the CRL measurement will be extremely reduced.
It’s not unusual for babies with anencephaly to have other major abnormalities, which might be detected at the same time.
Some babies with anencephaly will have significantly higher amniotic fluid levels.
What are the symptoms of anencephaly?
Babies born with anencephaly usually display a number of specific physical traits, such as:
- The head is missing bones at the back or sides
- Skull defects will be symmetrical
- Large areas of the brain are missing
- Folding of the ears
- Cleft palate
- Congenital heart defects.
What are the risks of anencephaly?
Sadly, there is no way to treat anencephaly; it is a fatal condition. Most babies with anencephaly die during the pregnancy or pass away within a few hours of birth.
For those carrying a baby affected by anencephaly, there is a high chance of the pregnancy ending in miscarriage, still birth or the baby being born prematurely.
Treatment for anencephaly
Unfortunately, there is no treatment or cure for anencephaly.
Can a baby with anencephaly survive?
A baby born with anencephaly is likely to pass away a few hours after birth. During this time, healthcare professionals work compassionately with families to create keepsakes and memories, and help families say goodbye to their babies.
Babies with anencephaly are born with large parts of the brain missing; they are often without the cerebellum and cerebrum. These areas of the brain are responsible for thinking, seeing, hearing, touch, movement, balance, and coordination.
Anencephaly will therefore result in significant developmental disabilities. Babies born with the condition will have no awareness of what is happening. They’re usually born blind and deaf and unconscious. The outlook is extremely poor.
Does anencephaly affect the mother?
There are several increased risks in pregnancy for a mother carrying a baby with anencephaly.
Research predicts that about 25% of anencephaly cases will have excessive fluid levels surrounding the baby; this is a condition known as polyhydramnios.
The condition can cause increased stretching of the uterus, which can be uncomfortable for the mother, and can also increase the risk of Preterm Birth.
The high fluid levels also increase the likelihood of the baby being in a breech or transverse position, which might make cesarean birth necessary.
In extreme cases, it might be necessary for the mother to undergo a procedure known as amnio-drainage, where an amniocentesis is performed to remove excess fluid from the amniotic sac.
Can anencephaly babies donate organs?
For some families whose babies have passed away, the idea of organ donation can bring them some comfort in their sadness, knowing that their baby’s organs have helped save another baby’s life.
It’s important to consider that organs from babies with anencephaly might be smaller than usual, or might not be fully formed. That means it might not be possible for their organs to be donated.
If you have specific questions about organ donation, speak to your healthcare provider, who’ll be able to support you in your decisions.
How can I reduce the chances of anencephaly?
Women of childbearing age can significantly reduce the chances of anencephaly by ensuring they reach the recommended daily dose of folic acid, before and during early pregnancy.
This can be achieved by taking 400 mcg folic acid daily, or by eating enough foods that contain naturally occurring folate, or foods with folic acid fortification.
Folic acid supplementation is usually recommended to all women of childbearing age, pre-conceptually and during the first 12 weeks of pregnancy, as a form of prevention of neural tube defects.
It’s important to recognize that anencephaly and spina bifida, as well as other neural tube defects, typically occur during the 3rd and 4th week of pregnancy – usually, before most women even realize they’re pregnant.
If you’re planning a pregnancy, it’s a good idea to make sure you’re already getting enough folic acid.
Since the U.S began fortifying grains with folic acid, there’s been a 28% decrease in pregnancies affected by neural tube defects.
How can I prevent anencephaly?
Not all cases of anencephaly can be prevented; however, you can reduce your chances of the condition by:
- Taking folic acid supplements before pregnancy and up to 12 weeks
- Avoiding certain medications. Speak to your healthcare provider to check that your medications are safe for pregnancy
- Avoid saunas and hot tubs – especially in early pregnancy
- Manage any underlying health conditions, such as diabetes and epilepsy.
What happens next?
Receiving a diagnosis for a birth defect, such as anencephaly, is undoubtedly devastating for families.
Allow yourself enough time and space to feel and explore all the emotions that come with it. It’s normal for you to feel a mix of different emotions at different times.
Some women will choose to continue with the pregnancy; some might opt to end the pregnancy early with a pregnancy termination (abortion).
Anyone facing such a decision should be counseled in depth, so that an informed decision regarding their care can be made. Patients should be fully informed about the specific condition affecting their babies, and about the potential increased maternal risks of continuing with a pregnancy for a non-life expectant baby.
Whatever you decide to do, it is a huge decision. Don’t feel rush or pressured into making a decision before you’re ready, and explore all options before deciding anything.
There are no right or wrong decision; each individual’s reasoning and choice will be different.
