How is anencephaly diagnosed?

During pregnancy, your healthcare provider may order tests to look for signs that might indicate a neural tube defect. Providers can also diagnose anencephaly at birth based on the newborn’s appearance. Prenatal tests for anencephaly include:

  • Quad marker screen: This blood test checks for neural tube defects and genetic disorders. Your provider takes a sample of your blood and sends it to a lab for testing. One of the tests in the quad marker screen is for alpha-fetoprotein (AFP). The AFP test detects higher levels of this protein. The baby’s liver makes AFP, and high levels leak into the mother’s blood if anencephaly is present.
  • Ultrasound: Using sound waves, this imaging test produces pictures of your unborn baby. Your provider uses an ultrasound (sonogram) to look at the baby’s skull, brain and spine.
  • Fetal magnetic resonance imaging (MRI): To see the brain and spine in greater detail, your provider may order this imaging test. An MRI uses high-powered magnets to produce images of tissues and bones.
  • Amniocentesis: Your provider inserts a thin needle into the amniotic sac (the fluid-filled bubble around the baby in the womb) and withdraws some fluid. A lab checks the amniocentesis fluid for high levels of AFP and an enzyme called acetylcholinesterase. Either of these substances may mean a baby has a neural tube defect.

Last reviewed by a Cleveland Clinic medical professional on 08/18/2020.

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