Anencephaly

Anencephaly is a serious birth defect in which a baby is born without parts of the brain and skull. This is a type of neural tube defect. As the neural tube forms and closes, it helps shape the baby's brain and skull (upper neural tube), spinal cord, and spinal bones (lower neural tube).

Anencephaly occurs when the upper part of the neural tube does not close completely. This often results in a baby being born without the front part of the brain (forebrain) and the thinking and coordinating part of the brain (cerebrum). The rest of the brain is often not covered by bone or skin.

Causes and prevention

The cause of anencephaly in most infants is unknown. Some children have anencephaly due to changes in their genes or chromosomes.

Getting enough folic acid before and during early pregnancy can help prevent neural tube defects such as anencephaly. If you are or could become pregnant, take 400 micrograms (mcg) of folic acid every day. If you have ever had a pregnancy related to a neural tube defect, you may want to discuss with your doctor the possibility of taking a higher dose of folic acid before and during early pregnancy.

To get the recommended 400 micrograms of folic acid per day, a woman of childbearing age can take folic acid supplements or eat folic acid-fortified foods, or both, depending on her dietary habits.

If you are pregnant or planning to become pregnant, talk to your doctor about how to increase your chances of having a healthy baby.

Diagnosis

Anencephaly can be diagnosed during pregnancy or after the baby is born.

During pregnancy

During pregnancy, screening tests (prenatal tests) are done to check for birth defects and other conditions. Anencephaly may cause an abnormal result on a blood or serum screening test or may be detected on ultrasound.