Alpha fetoprotein (AFP) is a protein produced by the liver and yolk sac of a fetus. AFP has no normal function in adults. The alpha fetoprotein test (AFP) is a blood test performed to measure, diagnose, or monitor fetal distress or fetal abnormalities. It can also detect some liver disorders and some cancers in adults.

During pregnancy, this test, along with the examination of amniotic fluid (amniocentesis), can help detect fetal spinal bifida or other defects of the fetus' neural tube.

The AFP test involves taking a blood sample. Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand.

Usually, there is little pain associated with a blood drawing. When the needle is inserted to draw blood, some people feel moderate discomfort, while others feel only a prick or stinging sensation.

There are few risks with this test:

• Excessive bleeding.
• Fainting or feeling lightheaded.
• Hematoma (blood accumulating under the skin).
• Infection (a slight risk any time the skin is broken).
• Multiple punctures to locate veins.

Normal AFP levels for men for for non-pregnant women are less than 300 nanograms per milliliter.

Greater-than-normal levels of AFP in men and non-pregnant women may indicate:

• cancer in testes, ovaries, biliary (liver secretion) tract, stomach, or pancreas
• cirrhosis of the liver
• liver cancer
• malignant teratoma
• recovery from hepatitis

During pregnancy, increased levels of AFP may indicate:

• Fetal defects.
• Spina bifida.
• Anencephaly.
• Omphalocele.
• Tetralogy of Fallot.
• Duodenal atresia.
• Turner's syndrome.
• Intrauterine death.