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Alpha Feto-Protein (AFP) Blood Test in Pregnancy

Last updated Feb. 27, 2019

The AFP Blood Test in Pregnancy is a screening test and not a diagnostic test; this means that the test is performed to determine the apparent risk for certain congenital abnormalities, such as spina bifida or chromosomal disorders, and not to confirm any diagnosis.


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

  • AFP Blood Test in Pregnancy
  • Maternal Alpha-Fetoprotein Blood Test
  • Maternal Serum Alpha-Fetoprotein Screening (MSAFP) Test

What is Alpha Feto-Protein Blood Test in Pregnancy? (Background Information)

  • Alpha feto-protein 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
  • In majority of healthy men and healthy non-pregnant women, alpha feto-protein (AFP) is not detectable or is detectable at very low levels
  • 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
  • Increase in alpha fetoprotein to above normal levels may be associated with the following conditions during pregnancy. Elevated AFP may either involve the expectant mother or the developing child
    • Neural tube defects such as spina bifida
    • 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
    • Presence of methylenetetrahydrofolate reductase gene (MTHFR gene) variant that may result in MTHFR gene deficiency disorder: A subset of women with this deficiency disorder have elevated AFP
    • Tumors in the pregnant woman (usually affecting the ovary) or the developing baby that may include yolk sac tumor (endodermal sinus tumor) or other germ cell tumors
    • Multiple gestations, such as pregnancy involving twins or triplets
  • Rarely, the levels of alpha fetoprotein may be below normal in conditions such as:
    • Down syndrome or trisomy 21
    • Edward syndrome or trisomy 18
    • Diabetes
  • The Alpha Feto-Protein (AFP) Blood Test in Pregnancy measures the amount of alpha feto-protein in blood during pregnancy. The test can be a stand-alone test or performed as part of triple screen (AFP, hCG, and uE3) or quad screen test (including inhibin A hormone)
  • The AFP Blood Test in Pregnancy is a screening test and not a diagnostic test; this means that the test is performed to determine the apparent risk for certain congenital abnormalities, such as spina bifida or chromosomal disorders, and not to confirm any diagnosis

What are the Clinical Indications for performing the Alpha Feto-Protein Blood Test in Pregnancy?

Clinical indicators for performing the Alpha Feto-Protein (AFP) Blood Test in Pregnancy include:

  • The test is typically performed as part of the triple screening (or quad screening) test during 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 either in the expectant mother or fetus

The AFP Blood Test in Pregnancy is usually done in the fourth month of pregnancy, typically between weeks 16 and 18.

How is the Specimen Collected for Alpha Feto-Protein Blood Test in Pregnancy?

Following is the specimen collection process for Alpha Feto-Protein (AFP) Blood Test in Pregnancy:

Sample required: Blood

Process of obtaining blood sample in adults:

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected, by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal
  • OR, a finger-stick method (pricking one’s finger) may be used for obtaining a sample of blood

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

What is the Significance of the Alpha Feto-Protein Blood Test in Pregnancy Result?

The significance of Alpha Feto-Protein (AFP) Blood Test in Pregnancy 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
    • 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)
    • Methylenetetrahydrofolate reductase deficiency disorder
    • Premature detachment of the placenta or placental abruptio
    • Presence of germ cell tumor such as yolk sac tumor
    • Twins, triplets, or other multiple pregnancies
  • Low levels of alpha fetoprotein may indicate:
    • Down syndrome
    • Edward syndrome
    • Gestational diabetes

Note:

  • In some cases, the test can be false positive, meaning that the result is abnormal even while the growing fetus is healthy. Sometimes, this may be because the initially assessed due date for delivery of the baby is inaccurate (it may have to be recalculated)
  • 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 amniocentesis (a medical procedure that involves removal of a small amount of amniotic fluid from the amnion for prenatal diagnosis)
  • If the AFP test is abnormal, then genetic counseling may be recommended by the healthcare provider
  • 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:

  • Elevated levels of alpha feto-protein in women may be also due to non-pregnancy related conditions, which get incidentally detected during pregnancy. In such cases, it is important to note that the fetus is generally healthy and fine

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?


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