How is anencephaly diagnosed?

Prenatal tests for anencephaly include:

  • Blood tests: Tests may show high levels of alpha-fetoprotein, a protein produced by the immature liver cells of the fetus.
  • **Amniocentesis: A small amount of fluid is withdrawn from the amniotic sac using a long needle that is inserted through the abdomen. The fluid can be analyzed to measure the levels of alpha-fetoprotein and acetylcholinerase. Higher-than-normal levels are linked to neural tube defects, such as anencephaly. **
  • Ultrasound: This imaging test uses high-frequency sound waves and a computer to make an image (sonogram) of the developing fetus. Abnormalities linked with anencephaly can be seen on the sonogram.
  • Fetal MRI: This imaging test uses a magnet to generate an image of the developing fetus. The brain and its various structures can be seen in more detail than the ultrasound alone.

Any of these procedures may be performed between the 14th and 18th weeks of pregnancy. The fetal MRI can be performed at any point of the pregnancy.

After a baby with anencephaly is born, the diagnosis is more apparent since the abnormalities of the skull can be easily seen. Bones around the front and sides of the head or the bony covering in the back of the head may be missing. Some brain tissue may be exposed when parts of the skull or scalp are missing.

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