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Amniotic Fluid Analysis for Alpha Feto-Protein (AFP)

Last updated Feb. 27, 2019

Approved by: Krish Tangella MD, MBA, FCAP

The Amniotic Fluid Analysis for Alpha Feto-Protein (AFP) is performed to measure the amount of alpha feto-protein in amniotic fluid during pregnancy.

What are the other Names for this Test? (Equivalent Terms)

  • Alpha Fetoprotein Amniotic Fluid Test
  • Amniotic Fluid Analysis for AFP
  • Amniotic Fluid Test for Alpha Feto-Protein

What is Amniotic Fluid Analysis for Alpha Feto-Protein? (Background Information)

  • Alpha feto-protein (AFP) is a form of serum protein similar to albumin, the most abundant protein in blood. It is produced by a developing fetus in the liver, yolk sac, and the gastrointestinal tract, during pregnancy
  • A low level of alpha feto-protein in pregnancy is normal, which may slightly increase during the course of a normal pregnancy. However, abnormally high levels of AFP may be a cause of concern and be indicative of various conditions that need further testing
  • AFP levels are determined as part of triple screen or quad screen test or as a stand-alone (independent) test. Usually, amniotic fluid levels test are performed as a follow-up to abnormal AFP blood levels in a pregnant women. In some cases, the healthcare provider may recommend an abdominal ultrasound or amniocentesis
  • Increase in alpha fetoprotein to above normal levels may be associated with the following conditions involving the developing child:
    • Neural tube defects such as spina bifida
    • Anencephaly: A fetal abnormality in which the brain, skull, and scalp remains underdeveloped
    • Birth defects such as gastroschisis and omphalocele
    • Placental abruption: A premature detachment of the placenta, either fully or partially, from the walls of the uterus, before the baby is delivered
    • Tumors in the developing baby that may include yolk sac tumor (endodermal sinus tumor) or other germ cell tumors
  • Rarely, the levels of alpha fetoprotein may be below normal from the expected AFP levels for gestational age (i.e., duration/stage of pregnancy). Such conditions may include:
    • Down syndrome or trisomy 21
    • Edward syndrome or trisomy 18
  • The Amniotic Fluid Analysis for Alpha Feto-Protein (AFP) is performed to measure the amount of alpha feto-protein in amniotic fluid during pregnancy

What are the Clinical Indications for performing the Amniotic Fluid Analysis for Alpha Feto-Protein?

Clinical indicators for performing the Amniotic Fluid Analysis for Alpha Feto-Protein (AFP) include:

  • As a follow-up testing of abnormal AFP blood levels in pregnancy
  • Suspicion of neural tube defects, such as spina bifida, in the developing fetus
  • A family history of certain genetic disorders such as Down syndrome or Edward syndrome
  • Presence of yolk sac tumor in the fetus

Amniotic fluid analysis is usually performed in the 2nd and 3rd trimester.

How is the Specimen Collected for Amniotic Fluid Analysis for Alpha Feto-Protein?

Following is the specimen collection process for Amniotic Fluid Analysis for Alpha Feto-Protein (AFP):

Sample required: Amniotic fluid

Process of obtaining amniotic fluid sample in pregnant women (amniocentesis):

  • A local anesthetic is applied to the site of amniocentesis
  • A needle is inserted into the mother’s abdominal wall, through the uterus and into the amniotic sac
  • Ultrasound imaging is used to guide the needle as it punctures the sac, at a location away from where the baby is
  • Approximately 20 ml of amniotic fluid is obtained, and the needle is withdrawn

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Amniotic Fluid Analysis for Alpha Feto-Protein Result?

The significance of Amniotic Fluid Analysis for Alpha Feto-Protein (AFP) is explained.

  • A negative result (i.e., normal result) usually means that the fetus is healthy
  • High levels of alpha fetoprotein may indicate:
    • Spina bifida or other neural tube defects
    • Anencephaly or absence of part of the brain and skull in the fetus
    • Other developmental birth defects including gastroschisis (when parts of the intestines of the fetus are seen outside the abdomen) and omphalocele (an abdominal wall defect in the fetus)
    • Premature detachment of the placenta or placental abruptio
    • Presence of germ cell tumor such as yolk sac tumor
  • Low levels of alpha fetoprotein may indicate:
    • Down syndrome
    • Edward syndrome


  • In some cases, the test can be false positive, meaning that the result is abnormal even while the growing fetus is healthy
  • Having a positive test result may not indicate the presence of a congenital abnormality. It only indicates a higher risk for the same
  • The physician may recommend additional tests to determine clinical management. Such additional measures may include repeating the tests, ultrasound of abdomen, and triple (or quad) screen test
  • Some of the factors that influence AFP levels include race, weight, and diabetes

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Due to the risks involved with amniocentesis, the test is not performed routinely in all pregnancies

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

What are some Useful Resources for Additional Information?

References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Feb. 27, 2019
Last updated: Feb. 27, 2019