A baby with anencephaly is missing parts of the brain, including skull bones. This makes survival difficult. Most infants die before birth or within a few days after birth.
Doctors do not know what causes anencephaly. But they do know that women who are expecting a baby should take folic acid supplements daily. Folic acid can help prevent neural tube defects like anencephaly.
Causes
Babies with anencephaly are missing the top of their skull and parts of the brain. Without a functioning cerebrum, these babies cannot survive. The majority of infants with anencephaly are stillborn or die soon after birth.
Several factors can lead to anencephaly. The most common is a lack of folic acid during pregnancy. Folic acid is a vitamin that helps the neural tube close correctly. It is found in foods and most prenatal vitamins. Not getting enough folic acid can increase the chances of having a baby with anencephaly or other neural tube defects, like spina bifida. Women who are at higher risk include those who have a history of spina bifida in their family, older age at the time of conception, and taking certain medications, including anticonvulsants used to treat seizures, bipolar disorder, or migraines, such as phenytoin and carbamazepine.
Other causes of anencephaly include genetic disorders and environmental exposures to chemicals that interfere with normal development. Anencephaly occurs in about one in a thousand pregnancies. The condition is caused when the upper end of the neural tube does not close correctly or reopens during early embryogenesis, leaving the brain and spinal cord exposed to amniotic fluid.
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Anencephaly can be diagnosed during the pregnancy through a blood test and ultrasound exam, or at birth. A physical exam can confirm the diagnosis by observing the absence of the calvarium (the top of the skull) and parts of the brain and skull.
During the ultrasound, high levels of a protein called alpha-fetoprotein can indicate anencephaly and other neural tube defects. A procedure called amniocentesis can also be done during pregnancy to look at a sample of the fluid surrounding the fetus (amniotic fluid) for markers of abnormal development, such as high levels of the liver protein acetocholinesterase and the enzyme phosphodiesterase. A sample of amniotic fluid can also be looked at with a microscope for the presence of neural tube defects.
Doctors may also use high-frequency sound waves to create pictures of the fetus on a computer screen, a technique called sonography. These images are called ultrasound scans or sonograms. The team caring for you during your pregnancy will talk to you about your options if your baby has anencephaly. Usually, this will include considering continuing the pregnancy to see if your baby might be able to donate some of their organs after birth.
Diagnosis
Many babies with anencephaly are stillborn or die shortly after birth. Occasionally, the condition is diagnosed during pregnancy through routine ultrasound or blood screening. A woman who is at risk for this type of neural tube defect may have amniocentesis, in which a doctor inserts a needle into the amniotic sac to collect a sample of the fluid around the baby. The doctor then tests the fluid for high levels of a protein called alpha-fetoprotein or acetylcholinesterase, which indicate that there is a problem with the neural tubes. In addition, a fetal magnetic resonance imaging (MRI) scan can show missing parts of the skull or brain.
The MRI test uses a magnetic field and radio waves to produce detailed images of the brain. This test is usually done between the 14th and 18th weeks of gestation. If the results suggest that the anencephaly is due to a lack of folic acid, the doctor will likely prescribe a supplement of folic acid for the mother. This can be taken by mouth orally or through injection into the vein.
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It is important to note that there are several other conditions that can cause the appearance of anencephaly, including amniotic band syndrome, giant encephaloceles, and placenta-cranial adhesions. Anencephaly can also occur as a result of having other malformations, such as limb (arms and legs) or digital (fingers and toes) amputations, abdominal wall defects, or spinal problems.
Anencephaly can be a difficult diagnosis for health care professionals to make. It is not common for this condition to be asymptomatic, so it can be hard to detect and diagnose in the early stages of a pregnancy.
However, when anencephaly is diagnosed, it is generally referred to as a “fatal defect.” Anencephaly is not compatible with life in the short or medium term, and most doctors will recommend termination of the pregnancy once the condition is diagnosed. If a pregnant woman is not comfortable with this decision, she may choose to discuss her options with a health professional or a support organization. These organizations can provide information about the various health and legal issues surrounding abortion or continuing a pregnancy with a neural tube defect.
Treatment
If an open neural tube defect (NTD) is detected in a pregnancy, such as with spina bifida occulta or anencephaly, it is usually recommended that the pregnancy be terminated. This is to prevent the fetus from reaching later gestational weeks, minimize physical and psychological trauma for the mother and her family, and reduce the risk of complications during labor and delivery.
Babies born with anencephaly are very fragile and cannot live long after birth. Unless there is a medical emergency, they will die within days or weeks after birth.
Most anencephaly cases are diagnosed by ultrasound or a blood test known as maternal serum alpha-fetoprotein screening. The blood test detects elevated levels of MSAFP, which indicate a developing neural tube defect. An ultrasound can also confirm the diagnosis of anencephaly, as well as other skull and brain abnormalities such as acrania.
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In some cases, a baby with anencephaly may survive to be born alive, but they will not have any functioning organs and are very fragile. If this happens, the specialist team will help plan your baby’s care and support options. They will discuss palliative care with you, which is when health professionals help to relieve symptoms and make people comfortable when a cure or treatment is not possible.
The specialist team will also explain the implications of your decision to continue or terminate the pregnancy. This is to help you understand the medical and ethical issues involved. For example, there are ongoing discussions about the definition of brain death in anencephalic patients and their candidacy for organ donation.
If you decide to continue your pregnancy, the specialist team will also support you through the process of finding out if your baby has anencephaly. They will refer you for a second scan to find out for sure if your baby has anencephaly. Public Health England and Shine have created a leaflet that gives information about the different options for care and support available after antenatal screening results are confirmed. It is called Antenatal Results and Choices (ARC). You can find out more about ARC by visiting the Public Health England website or calling the NHS helpline number.
Pregnancy complications
The condition anencephaly is when a large part of the brain and skull do not form. It is the most severe type of neural tube defect and accounts for half of all cases diagnosed prenatally. A baby with anencephaly usually dies in utero (stillborn) or only lives for a few hours or days after birth.
A baby with anencephaly will have a skull that looks like “Mickey Mouse ears” when viewed on ultrasound. The fetus will also have an exposed brain, and the tissue that would normally cover the brain is broken down by amniotic fluid, leaving no recognizable brain. It is believed that anencephaly develops from the earlier gestational stage of acrania, and as the pregnancy progresses, the exposed brain tissue is broken down by amniotic fluid until there is no recognizable brain at the end of the gestation.
The most common complication associated with anencephaly is intrauterine death (miscarriage). The risk of miscarriage is higher in women with anencephaly and those who have had a previous anencephaly or spina bifida. It is also increased if there is a family history of neural tube defects, such as spina bifida or anencephaly.
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If a woman is pregnant with anencephaly, she will need to discuss genetic counseling and the possibility of terminating the pregnancy. In some countries, anencephaly and spina bifida are screened for prenatally, and the frequency of termination of pregnancy (TOP) after a diagnosis of anencephaly or spina bifida is high.
The risk of having a child with anencephaly is reduced by taking folic acid prior to conception. This is recommended for all women planning a pregnancy, especially those with a family history of neural tube defects, including spina bifida and anencephaly. Folic acid is an important nutrient that helps to ensure the development of healthy nerves and spinal cord. It is found in many foods and can be taken as a dietary supplement or multivitamin. Folic acid is most effective when taken in the first trimester of pregnancy. Many food manufacturers fortify products with folic acid to help prevent neural tube defects.
