Definition

Anencephaly is a neural tube defect where the brain and skull fail to develop properly. The cerebrum (large brain) and cerebellum (small brain) are either underdeveloped or absent. Anencephaly is one of the more common neural tube defects, affecting 1 in 1,000 pregnancies. However, many of these pregnancies result in miscarriage, so the number of babies born with this condition is significantly lower.

Causes

Anencephaly is caused by various factors interacting during pregnancy. It generally occurs independently of other bodily system defects. One primary cause is a folic acid deficiency during pregnancy. This deficiency may be due to insufficient dietary intake of folic acid or the use of medications that reduce folic acid levels in the body, such as the anticonvulsant valproic acid.

Other causes include pre-pregnancy insulin-dependent diabetes mellitus, particularly if blood sugar levels are not well controlled.

Other factors include maternal hyperthermia (overheating), which can occur as a result of a high fever or bathing in hot water. Furthermore, damage to the amniotic wall can disrupt organ development, including the brain, resulting in anencephaly.

Genetic factors also play a role, as some families may carry genes that increase the risk of neural tube defects such as spina bifida (the spinal cord does not close completely) and anencephaly.

Risk Factor

Antenatal anencephaly risk factors are associated with maternal causative factors. Because anticonvulsant medications hinder the absorption of folic acid, their use by the mother may raise the risk of anencephaly. Additionally, folic acid supplements and insufficient nutrient intake can raise the risk of anencephaly. Because diabetes disrupts the production of proteins during organ formation in the fetus, prenatal diabetes in the mother can also raise the risk of anencephaly. Fever-induced or hot water/sauna-induced hyperthermia can disrupt neural tube closure, leading to anencephaly. Furthermore, taking too much vitamin A can have the same effect, leading to abnormalities in the formation of nerves.

Symptoms

A fetus with anencephaly cannot survive. In anencephaly, the neural tube fails to close, exposing the brain and spinal cord to amniotic fluid, which damages these structures. Consequently, the fetus lacks a functional cerebrum and cerebellum, essential for thinking, hearing, seeing, feeling emotions, and coordinating body movements. The fetus typically also lacks a complete skull.

Most pregnancies with anencephalic fetuses end in miscarriage. If the fetus survives to birth, the baby is usually stillborn or dies within hours or days after birth.

Diagnosis

Anencephaly can be detected during pregnancy. Laboratory tests that can be used to check for anencephaly are alpha-fetoprotein (AFP) tests in the mother or in the amniotic fluid. This test can be performed from the end of the first trimester to the second trimester. In anencephaly, increased AFP levels are found. This test is usually performed together with an acetylcholinesterase (AChE) test to prevent false positive results.

Ultrasonography (USG) is another test that can be performed during pregnancy. Based on the fetus's brain and skull development, new USG findings can identify anencephaly in the second trimester. Lack of amniotic fluid swallowing by the fetus can result in polyhydramnios, or an excess of amniotic fluid.

Anencephaly is visible after birth. Anencephaly is defined as the absence of both the skull bones that cover the brain and the brain itself. Skin may or may not cover the absence of this structure. The facial structure is generally normal.

Management

Anencephaly is a lethal condition, meaning it is certain to result in death. It is therefore not recommended to attempt any efforts to extend the baby's life. The family dealing with this condition is typically the focus of management. Family education regarding the fetus's condition is crucial if the condition is found during pregnancy. It is up to the family to decide whether to end the pregnancy or keep it going. However, from a religious and legal standpoint, special considerations are required in order to terminate a pregnancy. It is also not advised to use medications to prevent an early birth or Caesarean section when you are about to give birth because the risks outweigh the advantages. Before birth, a doctor can also talk about treatment planning.

If a geneticist or genetic counsellor is available, parents of a fetus with anencephaly may be referred for information regarding recurrence risk, prevention, screening, and diagnostic testing for future pregnancies or to assess family history. Genetic counsellors can help families deal with the complex psychosocial issues that come with this condition and can help families plan future pregnancies.

If the family was unaware of the condition while pregnant, additional emotional support and counselling are required. Parents often require more time to grieve and accept reality. The presence of family, friends, and religious leaders can be beneficial in many situations.

Families generally want to hold the baby, even if it is stillborn. In addition, families frequently want to photograph the baby. Wearing a hat or other head covering may be required to alleviate the fear of seeing the baby's head deformity. Sometimes parents or other family members want to see or touch the baby's head, which can help the person deal with their grief.

After birth, if the family is planning another pregnancy, taking folic acid supplements is highly recommended. The ideal intake of folic acid supplements is 400 mg per day to prevent neural tube defects in subsequent pregnancies.

Complications

The primary complication of anencephaly is death. Polyhydramnios, or an excess of amniotic fluid, is a possible pregnancy complication. Because the abdominal muscles are more stretched, the mother may feel uneasy. Premature birth is highly risky in this case.

In contrast, postterm pregnancy or pregnancy lasting longer than 42 weeks, is possible. In fetuses with anencephaly, the pituitary gland, which secretes hormones, is absent. In cases like this, birth can be induced in a variety of ways.

Prevention

Preventing anencephaly involves adequate folic acid intake before and during pregnancy. Women planning to conceive and those with a history of neural tube defects should take 4 mg of folic acid daily. For women with a normal pregnancy history or those who have never been pregnant, 400 micrograms of folic acid daily is recommended. Dietary folic acid availability is significantly lower than in supplements.

When to See a Doctor?

If you plan to conceive, consult a doctor to discuss folic acid supplementation to prevent neural tube defects. The doctor will conduct various examinations to prevent pregnancy complications for both mother and fetus. Inform the doctor if you have a history of anticonvulsant or other medication use, as dosage adjustments may be necessary before and during pregnancy.

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