Anencephaly: what it is, causes, diagnosis and risk factors


What is anencephaly?

Anencephaly is a condition in which the baby is born with an underdeveloped brain and without the skullcap. It occurs because of a malformation of the neural tube , which occurs as early as the fourth week of embryonic development.

The condition is characterized by the absence of the brain and the skullcap (top of the skull), with a reduced presence of the cerebellum and meninges. All of these are extremely important parts of the brain, as they allow thinking, seeing, hearing, coordinating movements, among other functions. In the vast majority of cases, brain tissue is exposed, without even being covered by skin.

At birth, the baby may have normal functioning of the brain stem, part of the nervous system responsible for several involuntary activities. Therefore, some vital functions of the organism may function correctly, such as the ability to breathe, swallow and maintain the heartbeat.

However, these babies live in a vegetative state, since consciousness is the responsibility of the brain as a whole. In any case, anencephaly remains a lethal pathology that confers a short life span outside the uterus.

This is not a common condition, but occurs once every 1,000 ~ 10,000 births (depending on the region where the statistical survey was carried out), being more common in Caucasian (white) female babies. In Brazil, there are about 3 thousand cases per year, making the country the 4th with the highest incidence of cases of anencephaly.

What causes anencephaly?

Anencephaly is the result of a malformation in a structure called “neural tube”, which occurs around the fourth week of pregnancy (between the 20th and 30th day).

At that time, the embryo consists of 3 cell layers that give rise to different organs. The ectoderm, one of these layers, is responsible for the formation of the nervous system. This layer receives signals for the formation of an area known as a “neural plate”.

Over time, this plaque creates wrinkles and begins to fold, joining the two sides together, forming a cylinder. This cylinder is called a neural tube and it is from there that the cerebral hemispheres that form the brain as we know it are formed.

In the case of anencephaly, there is a problem in this process of “closing” the neural tube. In this way, the brain tissue is exposed to the amniotic fluid, which in turn, degenerates it. It is common for children with this condition to also have the so-called spina bifida, in which some vertebrae do not form and the spinal cord protrudes out of the bones.

Unfortunately, science is not yet able to explain why this malformation occurs. Several experts believe that this is a multifactorial condition, in which genetic, environmental, seasonal and even geographical issues have an influence.

Genetic factors

Genes linked to the processing of folic acid in the body, such as those responsible for the enzyme methylenetetrahydrofolate reductase (MTHFR), seem to be related to cases of anencephaly. However, the presence of these genes alone does not determine the development of the condition.

Despite this, there are no signs that anencephaly is hereditary: there are few cases that occur several times in the same family. Even so, parents who have already had a child with anencephaly are at a slightly higher risk of developing the same problem in future pregnancies.

Amniotic band syndrome

Also known as amniotic bridging syndrome , this syndrome is characterized by the formation of “pieces” – called “bands” or “bridles” – of tissue similar to that of the amniotic pouch, which are usually wrapped around the baby’s fingers, arms or legs.

When this happens, those parts of the baby stop receiving oxygen and die. Thus, the baby is born without fingers or even without a full limb.

Very rarely, a band is wrapped around the face or head, leading to malformations such as cleft palate or anencephaly.

Risk factors

Despite not knowing why anencephaly happens, it is known that some factors contribute to its development:

Subsequent pregnancy

Parents who have already had an anencephalic baby are 2.5% to 4% more likely to have another baby with the problem in the next pregnancies.

Diabetic mothers

Apparently, diabetic women are 6 times more likely to have an anencephalic baby.


The incidence of anencephaly is higher in babies of very young or older mothers.

Lack of folic acid

It is known that the ingestion of low levels of folic acid is a risk factor for several malformations, including anencephaly.


Women who use epilepsy medications are more likely to have an anencephalic child.

Exposure to toxins

Some doctors associate anencephaly with exposure to certain toxic substances, such as chromium, lead, mercury and nickel.


Very high body temperatures are related to an increased likelihood of having an anencephalic baby, so it is important that the mother avoids very hot baths, saunas and other situations in which she can overheat the body.


During pregnancy, the mother does not have any specific symptoms that the baby is developing a malformation.

The baby, at birth, has an abnormal shape of the head: the lack of the skullcap and the brain is evident. He has no forehead, his ears are malformed and low, and he has a short neck.

Various bones of the face are deformed, changing the size and shape of certain parts of the head. It may have a cleft palate and protruding eyeballs due to malformations in the eyelids (the part where the eye “fits” in the face).

The baby is blind, deaf and unconscious. Depending on how much the brain has managed to develop, the child can still “hear” through touch, since loud sounds cause physical vibrations of the air that can be felt. In these cases, unfortunately, the baby is also able to feel pain.

Even if there is a brain stem, the lack of a functioning brain makes consciousness impossible.

Sometimes there are also congenital cardiac malformations.

How is anencephaly diagnosed?

Generally, the diagnosis is made during the prenatal period, through the ultrasound exam after 12 weeks of gestation. This examination is part of the prenatal routine and reveals images of the baby’s development during pregnancy.

As the skull is not yet fully formed until 12 weeks, the diagnosis of anencephaly can only be made after this period.

If the woman has not had prenatal care, the diagnosis is made at the time of delivery by physical examination of the baby.

Laboratory tests

Upon finding signs of anencephaly on ultrasound, the doctor may order a dose of alpha-fetoprotein in maternal serum or amniotic fluid after 13 weeks of gestation. Anencephaly cases are related to a high level of alpha-fetoprotein.

Maternal serum is drawn from the blood as in a normal blood test. Amniotic fluid, on the other hand, is extracted by means of an amniocentesis , a procedure that consists of a puncture that goes to the amniotic bag and takes a small sample of the liquid for analysis.

Complementary exams

After confirming the diagnosis, the doctor may order an MRI to identify other comorbidities, such as spina bifida, congenital heart disease or changes in the genito-urinary system.

Other malformations

In general, anencephaly happens in isolation, that is, there are no other malformations that accompany it. However, when this happens, the most common types of malformations are:

  • Spina bifida;
  • Congenital heart defects;
  • Cleft palate;
  • Diaphragmatic hernias;
  • Spinal cord syndrome;
  • Musculoskeletal and gastrointestinal abnormalities;
  • Abnormalities of the urinary tract.

Prognosis: can the anencephalic survive?

Unfortunately, it is not possible to survive with anencephaly . 50% of deaths from anencephaly still occur inside the womb. 99% of babies who manage to survive childbirth die soon after, and the other part survives only for a few hours or days.

There are cases in which babies manage to survive months and even reach two years. However, experts do not believe that it is anencephaly, but other malformations that promote a longer life expectancy.

Abortion in case of anencephaly

In Brazil, the termination of pregnancy of anencephalic fetuses has been permitted by the Supreme Federal Court since April 12, 2012. Before this date, mothers had to go to court to obtain authorization.

Today, mothers who do not want to continue the pregnancy after the discovery of the condition must submit, to the competent authority, a detailed ultrasound with 3 photos of the fetus, detailing the skull, signed by 2 different doctors.

Mothers who do not want to have an abortion may choose to donate the baby’s organs if the baby is born alive and can survive a few hours. However, they should be advised of the risks of maintaining this pregnancy.

Anencephaly and microcephaly

Although the two conditions directly affect the baby’s brain and skull, anencephaly and microcephaly are quite distinct malformations.

At first, the brain cannot even be properly formed. In the second, the brain is formed, but it is smaller. While the anencephalic cannot survive after birth, the microcephalic baby will be able to live outside the womb, with some limitations.

According to the Federal Senate, there are 3 types of brain malformations: lethal, severe and minor. The lethal ones are those incompatible with life, while the severe ones refer to the types that cause early death, abnormalities or serious stops in the child’s physical or mental development. The smallest type is when the damage still allows a certain life span.

Thus, it can be said that anencephaly is a lethal malformation, while microcephaly is a severe malformation. However, it is worth remembering that growth retardation, cognitive problems and even neurological damage that can cause epilepsy and autism are common in microcephalic babies.


In 2015, due to the outbreak of microcephaly related to the Zika virus, a debate was ignited about the possibility of abortion of microcephalic babies. Judicially, microcephaly does not justify abortion in the same way as anencephaly, since the baby’s condition is compatible with life.

Therefore, it is necessary to make it clear that abortion of fetuses with microcephaly is illegal , unlike anencephalic babies.

Is anencephaly curable? And treatment?

There is no cure or even any type of treatment that can save the life of the baby born with anencephaly. When the patient is born and able to breathe, the hospital usually offers ventilatory support to try to prolong life, being only a palliative treatment.

However, the family can opt for psychological treatment, since the loss of a long-awaited baby can be a traumatic situation. If the mother wants to have other children, for example, she may lose hope, even though she has a chance of having a healthy baby.

With the support of a psychologist and psychiatrist, both the mother and the family can receive the emotional support necessary to try again and ease the pain of having lost a child.

Living with the news

After diagnosis, many parents may have problems dealing with the news that their baby is anencephalic. The grieving process can begin both before delivery and shortly after, when reality comes to the fore.

Depending on the gestational age, parents may choose to have an abortion or not. When the continuation of pregnancy puts the mother’s life at risk, it is very likely that doctors will remove the baby early, even if she wants to continue with the pregnancy.

When the mother decides to continue the pregnancy until the end, many parents like to hold the baby in their arms after delivery, even if the baby died during the procedure. For some people, seeing the baby after birth helps them cope with the entire grieving process.

There are parents who imagine the malformations worse than they really are, so getting in touch with the baby can help to change the sad image that the parents created in their heads. Some families even ask to take a photo with the baby, using a cloth or hat to minimize the impact of the malformation.

If the parents have chosen a name for the baby, it is also important that doctors treat the child by that name.

Not infrequently, parents feel a part of guilt about their child’s malformation. However, most of the time the parents could not have done anything to prevent the problem. In such cases, genetic counseling is recommended to help the family understand the situation.

Complications in childbirth

At delivery or during pregnancy, a mother carrying an anencephalic child may experience some complications. Are they:

Accumulation of amniotic fluid

Since most anencephalic babies have reduced swallowing capacity, amniotic fluid – used to feed the baby during pregnancy – is accumulated inside the uterus.


During delivery, due to the accumulation of amniotic fluid, the uterus may not contract, which gives rise to possible bleeding. This condition puts the mother’s life at risk.

Anomalous positions

Not infrequently, anencephalic fetuses assume positions outside the conventional for the time of delivery. Healthy babies tend to turn upside down, leaving their head positioned towards the vaginal canal.

Another problem is that the skull – which is not completely formed in the anencephalic – is extremely important for the time of delivery, since it is precisely he who opens the space for the passage of the entire body of the baby in the vaginal canal.

Other complications

Some other examples of complications that may occur during pregnancy are hypertension and displacement of the placenta.


Often, it is not known what exactly can be done to prevent anencephaly, other than avoiding risk factors for the development of the disease. However, this is not always possible. Some tips are:

Folic acid supplementation

The folic acid is a substance that helps prevent malformations in general and its supplementation before and during pregnancy can help in the case of mothers who have higher chances of gestating an anencephalic child.

It is recommended to ingest 400 micrograms of folic acid per day, which can be taken either through food or as a supplement.

Avoid contact with toxic substances

Women who work in contact with toxic substances, such as lead and mercury, must reconsider their work environment before even trying to conceive. This is because malformation occurs in the first few weeks, while the mother is often not even aware of the pregnancy.

Stopping or using medications

Antiepileptics are related to greater chances of anencephaly. Depending on the situation, suspending the use of these drugs is contraindicated, especially in case of severe epilepsy.

However, patients using these drugs for their mood-stabilizing effect may need to contact their psychiatrist and request another, safer medication for pregnancy.

Although rare, the diagnosis of anencephaly can be emotionally devastating for the family. Share this text so that more people are aware of the condition and what it does to the baby.

If you are trying to get pregnant, always remember to keep your appointments with the gynecologist up to date!