Anencephaly

Anencephaly is a condition in which the skull and brain do not fully develop in human fetuses. Anencephaly is very rare and occurs in about only three in every ten thousand births. This disorder is almost always fatal before or just after birth. Anencephaly cannot be treated. It is a type of neural tube defect. Researchers have identified some risk factors for anencephaly, but they do not fully understand why many cases of the disorder occur. Women can reduce the risk of their pregnancies being affected by anencephaly by taking higher doses of folic acid.

Background

Anencephaly is a type of neural tube defect (NTD). NTDs happen because the spinal cord or the brain does not form properly. They can develop with openings that can cause problems. NTDs usually occur very early in a fetus's development. The part of the fetus that will become the spinal cord begins as a flat area. Then the area rolls into a tube and becomes the neural tube. This typically occurs during the third or fourth week of development. The neural tube will develop into the spinal cord and the brain. If the neural tube does not close properly during development, the opening can cause problems in the developing brain and spinal cord. Two types of NTDs exist. Closed NTDs occur when skin covers the opening in the spinal cord. Open NTDs occur when the brain or the spinal cord is exposed. Anencephaly is an open NTD.

Overview

Babies born with anencephaly are usually born with portions of the brain, skull, and scalp missing. All infants born with anencephaly are born without all or part of the brain. Infants born with anencephaly are usually missing the front part of the brain, also called the forebrain. This is the part of the brain where thinking takes place. Other parts of the brain may be present. In some cases, infants born with the disorder can breathe and respond to touch and sound. However, they cannot gain consciousness. Some facial abnormalities can occur in infants with anencephaly in part because of missing parts of the skull. Other birth defects sometimes accompany anencephaly (about 20 percent of the time). Some infants with anencephaly also have heart defects, cleft palate, and folded ears.

Anencephaly is a fairly rare disease. It occurs in roughly three out of every ten thousand births. Yet, the exact number of pregnancies affected by anencephaly and other NTDs is unknown because some pregnancies affected by NTDs end in miscarriage. Anencephaly rates are higher among female infants than male infants. However, that might be because rates of miscarriage and stillbirth are higher among males.

The causes of anencephaly are usually unknown. However, women can reduce the risk of NTDs by potentially between 50 and 70 percent by increasing their intake of folic acid. Folic acid is a water-soluble B vitamin. Women can increase folic acid in their diets or they can take supplements. Most medical professionals advise women to take supplements to ensure they take in 400 milligrams of folic acid per day, which is the recommended amount for women who are pregnant or who are planning to become pregnant. Most prenatal vitamins have the amount of folic acid recommended for pregnant women. The neural tubes often form or begin to form before women realize they are pregnant; therefore, doctors often recommend that women take prenatal vitamins or other sources of folic acid before they begin to try to get pregnant. Women who have had previous NTD pregnancies are generally advised to take supplements with 4,000 milligrams of folic acid if they plan on becoming pregnant again. This extremely high dose is generally prescribed by doctors. In 1998, the US Food and Drug Administration (FDA) mandated that enriched cereal grain products be fortified with folic acid. This helped reduce the cases of anencephaly in the United States.

Although taking higher doses of folic acid may help reduce the risk of NTDs, medical professionals are unsure why many cases of anencephaly occur. A small percentage of cases seem to be caused by genetics. In about 90 percent of cases, neither parent of an infant with anencephaly has the disease in their family history. However, when parents have one pregnancy with anencephaly, they are more likely to have future pregnancies with the disorder. Some other cases may be caused by prescription drugs, such as diabetes medications, that a woman takes during pregnancy. Infants born to Hispanic mothers are at an increased risk for having anencephaly. The reason for this increased risk is not well understood. The causes of many cases of anencephaly are never known. Research is being done to better understand the causes of anencephaly so medical professionals can counsel their patients about more ways to reduce the risk.

Anencephaly can be diagnosed in a number of ways. The first is through a blood test. Tests that show a high amount of alpha-fetoprotein, a particular protein in a fetus's liver, may indicate anencephaly. Anencephaly can also be diagnosed through amniocentesis, which is a test that can be done during late phases of pregnancy. During this test, a small amount of amniotic fluid is taken from the amniotic sac, which is a bag of fluid where the fetus develops. The fluid contains fetal tissues, and the test can detect high levels of alpha-fetoprotein. Ultrasound, which is a noninvasive imaging test, gives medical professionals pictures of developing fetuses. These images can sometimes identify cases of anencephaly. Fetal MRI, which is another imaging test, can give more detailed pictures and either confirm or give an anencephaly diagnosis.

Anencephaly has no known treatments. Roughly 75 percent of infants with anencephaly are stillborn. Infants born living with the disorder often live for hours or days. Some infants have lived for weeks or months. Palliative care is often provided for the families of infants with the disorder. Medical teams often try to care for the families of those born with the disorder. Women who have pregnancies affected by anencephaly will often be prescribed high doses of folic acid and will sometimes receive genetic counseling.

Bibliography

"Anencephaly." Children's Hospital of Wisconsin, www.chw.org/medical-care/fetal-concerns-center/conditions/infant-complications/anencephaly/. Accessed 9 Mar. 2017.

"Anencephaly." Cleveland Clinic, 19 Jan. 2017, my.clevelandclinic.org/childrens-hospital/health-info/diseases-conditions/hic‗Anencephaly. Accessed 9 Mar. 2017.

"Anencephaly." Genetics Home Reference, Nov. 2014, ghr.nlm.nih.gov/condition/anencephaly. Accessed 9 Mar. 2017.

"Anencephaly." National Organization for Rare Disorders (NORD), 2012, rarediseases.org/rare-diseases/anencephaly/. Accessed 9 Mar. 2017.

"Facts about Anencephaly." Centers for Disease Control and Prevention, 9 Nov. 2015, www.cdc.gov/ncbddd/birthdefects/anencephaly.html. Accessed 9 Mar. 2017.

"Neural Tube Defects (NTDS)." Duke Molecular Physiology Institute, dmpi.duke.edu/neural-tube-defects-ntds. Accessed 9 Mar. 2017.

Noggle, Chad A. "Anencephaly." The Encyclopedia of Neuropsychological Disorders. Edited by Arthur MacNeill Horton, Springer Publishing Company LLC, 2012.

"Plan Ahead: Folic Acid Can Help Prevent Certain Birth Defects." Centers for Disease Control and Prevention, 11 Jan. 2017, www.cdc.gov/features/folicacidbenefits/. Accessed 9 Mar. 2017.