What Is Anencephaly? What Are the Symptoms? How Is It Treated?

Anencephaly: What Is It, Symptoms, and Treatment?

In this article, we will examine the details of this topic. Anencephaly is a fatal birth defect. It occurs when a fetus's brain and skull do not develop as expected in the womb. Babies born with this condition usually pass away within a few hours or a few days. The majority of these pregnancies end in miscarriage. Taking the recommended dose of folic acid before and during pregnancy can help reduce the risk of anencephaly.

What Is Anencephaly? Anencephaly is a birth defect (congenital disorder) where a baby is born without parts of the brain and skull. This condition affects the baby's nervous system, which includes the brain, spine, and nerves. It occurs during the first month of pregnancy when the neural tube—responsible for developing the brain, skull, vertebrae, and spinal cord—fails to develop expectedly or close properly. Therefore, anencephaly is classified as a cephalic disorder, specifically a neural tube defect.

The brain is essential for sustaining life; it controls body functions, emotions, and memory. Because anencephaly severely impacts brain development, infants born with it typically survive for only a few minutes, hours, or days. Most pregnancies affected by anencephaly end in miscarriage or stillbirth.

What Are the Types of Anencephaly? There are three types of anencephaly, all of which are fatal to the fetus:

• Meroanencephaly: The brainstem and midbrain are only partially developed. A portion of the brain is covered by skin and skull.
• Holoanencephaly: The brain does not develop at all. This is the most common type of anencephaly.
• Craniorachischisis: The brain, skull, and spine fail to develop. This is the most severe form of anencephaly.

How Common Is Anencephaly? Anencephaly is a common type of neural tube defect. Research shows it affects approximately 1 in every 1,000 pregnancies. However, because most pregnancies with anencephaly result in miscarriage, the condition affects only about 1 in 10,000 live births in developed countries.

Signs of Anencephaly Signs of anencephaly include:

• Elevated levels of alpha-fetoprotein (a fetal protein) detected in the biological mother's blood tests or amniotic fluid samples. This blood test is typically performed during the second trimester of pregnancy.
• Polyhydramnios (an excessive amount of amniotic fluid in the amniotic sac) visible during a prenatal ultrasound.
• Absence of parts of the skull and brain.
• Exposed brain tissue (lacking overlying skin or bone).
• A head circumference that is significantly smaller than expected.

A doctor will recommend various prenatal tests to screen for conditions like anencephaly during pregnancy.

Symptoms of Anencephaly The biological mother may not notice any symptoms until a blood test or ultrasound is performed. Newborns born with anencephaly lack the following functions:

• Consciousness (awareness)
• Sight
• Hearing
• Ability to feel pain

In all newborns with anencephaly, the cerebrum fails to develop. In those where the brainstem is present, reflex actions may occur, and they may automatically respond to touch. While these involuntary reactions might offer brief hope to families, they do not indicate that the newborn is conscious of touch or able to survive long-term.

What Causes Anencephaly? Anencephaly is caused by an issue during the formation and closure of the neural tube. The neural tube is a flat layer of tissue that folds into a tube. Different sections of the neural tube contribute to the development of different parts of the baby's body:

• Brain and skull (upper part of the neural tube)
• Spinal cord (middle part of the neural tube)
• Vertebrae (lower part of the neural tube)

Anencephaly occurs when the upper portion of the neural tube fails to close during embryonic development, specifically between the third and fourth weeks of pregnancy. As the fetus continues to develop, the forebrain and cerebrum do not form. Other parts of the brain may develop as expected, but they remain exposed without the protective layer of overlying skin or skull.

Is Anencephaly Inherited? Based on current medical knowledge, anencephaly is generally not inherited (it is not passed down through families). In the vast majority of cases, it occurs sporadically without any prior family history of the condition. However, if a family has previously had a child with a neural tube defect like spina bifida, the probability of having a baby with anencephaly increases. This risk rises to approximately 2% to 3%, which is about 20 times higher than for individuals without a prior history of neural tube defects.

Risk Factors for Anencephaly Certain medications and risk factors can increase the likelihood of having a baby with anencephaly or another neural tube defect. These include:

• Folic Acid Deficiency: Inadequate intake of folic acid (vitamin B9) during pregnancy increases the risk. Doctors often recommend taking a prenatal vitamin containing 400 micrograms (mcg) of folic acid both before and during pregnancy.
• Diabetes: Uncontrolled blood glucose levels can be dangerous to the developing fetus. Managing diabetes effectively helps reduce the risk of complications.
• Medications: Certain anti-seizure medications, such as phenytoin, carbamazepine, and valproic acid, can elevate the risk of neural tube defects. Some of these drugs are also prescribed for migraines and bipolar disorder. If pregnancy is planned, discuss current medications with a doctor before stopping any prescribed drugs.
• Opioid Use: Opioid use during the first two months of pregnancy can lead to neural tube defects. Opioids include illicit substances like heroin as well as prescription pain relievers such as hydrocodone.

How Is Anencephaly Diagnosed? During pregnancy, specific prenatal screening tests are performed to detect birth defects and other conditions that could affect fetal health. Prenatal tests capable of diagnosing anencephaly include:

• Quad Screen Test: This blood test screens for neural tube defects and genetic conditions. One of its four markers is the alpha-fetoprotein (AFP) test, which measures levels of a protein produced by the fetal liver. When anencephaly is present, high levels of AFP leak into the mother's bloodstream. The AFP test can also be performed on its own.
• Ultrasound: Using sound waves to capture images of the fetus, doctors evaluate the skull, brain, and spine.
• Fetal Magnetic Resonance Imaging (Fetal MRI): A doctor may order an MRI for a more detailed evaluation of the brain and spine using powerful magnetic fields.
• Amniocentesis: A thin needle is inserted into the amniotic sac to collect a sample of amniotic fluid. The laboratory checks the fluid for high levels of AFP and an enzyme called acetylcholinesterase. Elevated levels of either substance can indicate a neural tube defect.

If prenatal screening tests—including ultrasounds—are not performed during pregnancy, a doctor can diagnose anencephaly through a physical examination immediately after birth.

How Early Can Anencephaly Be Detected? A doctor can detect anencephaly as early as the first trimester, between the 8th and 12th weeks of pregnancy. On average, routine screenings for anencephaly are performed between the 18th and 20th weeks of gestation.

How Is Anencephaly Treated? There is currently no cure or standard treatment for anencephaly. Almost all infants born with anencephaly pass away within a few hours or days after birth. The neonatal healthcare team focuses on supportive palliative care, helping the family navigate the grieving process and say goodbye to their baby.

Prognosis of Anencephaly Anencephaly is a fatal condition with a poor prognosis. Most fetuses with anencephaly do not survive to term, resulting in miscarriage or stillbirth. Nearly all infants born alive succumb to the condition within minutes, hours, or days.

Does a Newborn with Anencephaly Feel Pain? Although it may appear that the newborn is experiencing distress or discomfort, infants with anencephaly cannot feel pain. Newborns who survive birth may seem to react to touch or sound, but these are involuntary brainstem reflexes rather than conscious perception. The cerebrum—the largest part of the brain responsible for thinking, feeling, sensory processing, and voluntary responses—is absent.

Can Anencephaly Be Prevented? While it may not always be possible to prevent anencephaly, the following steps can help reduce the probability:

• Adequate Folic Acid Intake: Take 400 mcg of folic acid daily, even if pregnancy is not actively planned. Because neural tube defects occur during the first month of pregnancy—often before a person realizes they are pregnant—starting folic acid prior to conception is critical. If a previous pregnancy was affected by a neural tube defect, consult a doctor for a higher prescribed dose of folic acid in subsequent pregnancies.
• Medication Review: Review all medications with a healthcare provider prior to conception, as certain drugs used for seizures or other conditions can cause birth defects.
• Managing Underlying Health Conditions: Work with a doctor to establish an optimal treatment plan for pre-existing conditions like diabetes to lower the risk of developmental defects.

Coping and Self-Care After Loss Learning that a baby has been diagnosed with anencephaly is profoundly difficult. The medical team provides compassionate support during the farewell process and offers follow-up care to assist the family's healing. Many individuals find strength in speaking with a mental health professional or joining a bereavement support group to share their feelings with others who have experienced similar losses. Feeling deep sorrow and grief is natural, and establishing a strong support network can help guide the grieving process.

When to Consult a Doctor If planning a pregnancy, schedule a preconception counseling appointment to address potential risk factors. If experiencing symptoms of a miscarriage—such as heavy vaginal bleeding, severe cramping, or intense back or abdominal pain—contact an obstetrician immediately.

Questions to Ask Your Doctor

• What steps should be taken to support health during pregnancy?
• Do any current medications pose a risk to a fetus if pregnancy occurs?
• Is folic acid supplementation necessary, and if so, at what dosage and frequency?
• What specific protocol should be followed if attempting to conceive after a previous pregnancy with a neural tube defect?
• Can you recommend a mental health specialist or support group experienced in perinatal loss?
• What self-care guidelines should be followed after suffering such a loss?

Even when every preventative recommendation for a healthy pregnancy is followed, severe birth defects can still occur. Receiving an anencephaly diagnosis is heartbreaking. Your healthcare team is there to answer your questions and support you through your loss. Seeking guidance from a mental health professional, connecting with support groups, or leaning on family and friends can offer comfort during this challenging time.