DefinitionAlpha fetoprotein (AFP) is a protein normally produced by the liver and yolk sac of a developing baby during pregnancy. AFP levels decrease soon after birth. AFP probably has no normal function in adults.A test can be done to measure the amount of AFP in your blood.See also: Quadruple screen
Alternative NamesFetal alpha globulin; AFP
How the test is performedA blood sample is needed. For information on how this is done, see: Venipuncture
How to prepare for the testThere is no special preparation.
How the test will feelWhen the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performedYour doctor may order this test to:Screen for problems in the baby during pregnancyDiagnose certain liver disordersScreen for and monitor some cancersDuring pregnancy, this AFP test can be done along with amniocentesis to help detect spina bifida or other birth defects in the developing baby.
Normal ValuesThe normal values in males or nonpregnant females is generally less than 40 micrograms/liter.The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What abnormal results meanGreater than normal levels of AFP may be due to:Cancer in testes, ovaries, biliary (liver secretion) tract, stomach, or pancreasCirrhosis of the liverLiver cancerMalignant teratomaRecovery from hepatitisDuring pregnancy, abnormal levels of AFP (as part of a quadruple screen) may be due to:Birth defects, including:
AnencephalyDuodenal atresiaGastroschisisOmphaloceleSpina bifidaTetralogy of FallotTurner syndromeGenetic disorders, including Down syndromeInaccurate due dateIntrauterine death (usually results in a miscarriage)Multiple pregnancy (twins, triplets, etc.)
What the risks areVeins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.Other risks associated with having blood drawn are slight but may include:Excessive bleedingFainting or feeling lightheadedHematoma (blood accumulating under the skin)Infection (a slight risk any time the skin is broken)
ReferencesSimpson JL, Otaño L. Prenatal genetic diagnosis. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics: Normal and Problem Pregnancies. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2007:chap 7.Lee P, Pincus MR, McPherson RA. Diagnosis and management of cancer using serologic tumor markers. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: Saunders Elsevier; 2006:chap 74.Cunningham FG, Leveno KJ, Bloom SL, et al. Prenatal diagnosis and fetal therapy. In: Cunningham FG, Leveno KL, Bloom SL, et al, eds. Williams Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2010:chap 13.