What Is An Alpha-Fetoprotein Test?
Alpha-fetoprotein is a commonly produced protein in the liver, the yolk sac, or the gastrointestinal tract of a developing baby. During the fetus’s development, some amount of this alpha-fetoprotein passes through the placenta and into the mother’s bloodstream. The alpha-fetoprotein blood test measures the level of alpha-fetoprotein in pregnant women.(1) It is usually done in the second trimester of the pregnancy, and too much or too little of this protein present in the mother’s blood could be an indication of a potential birth defect or some other medical condition of the fetus.(2)
In some cases, the alpha-fetoprotein test is also useful for adults who are not pregnant since even individuals who are not pregnant also have some amount of this protein present in their blood. However, the levels are usually very low. In people who are not pregnant, high levels of the alpha-fetoprotein are generally indicative of certain types of liver conditions.
What Is The Need For An Alpha-Fetoprotein Test?
An alpha-fetoprotein test is part of a routine screening test that is prescribed for expecting mothers between 14 to 22 weeks of pregnancy. The test is said to be most accurate when it is performed between the 16th and 18th weeks. This is why it is essential to keep track of the exact date when you become pregnant so that you are able to track the weeks correctly.
Alpha-fetoprotein testing is done as part of a quad screen, which is a diagnostic procedure that also tests the levels of:(3)
- The hormone human chorionic gonadotropin (HCG)
- Inhibin A, which is a hormone produced by the placenta (4)
- Estriol, which is a hormone produced by the baby’s liver and the placenta (5)
The quad screen results, your age, ethnicity, and other factors are used by doctors to determine the likelihood of your baby having a genetic birth defect. This type of screening is able to detect anomalies that can include neural tube problems such as spina bifida, as well as chromosomal abnormalities, such as Down’s syndrome. (6, 7)
The results of the alpha-fetoprotein test help doctors determine if there is a need for further tests for such conditions. However, getting a positive test result does not necessarily mean that your baby will be born with some type of birth defect.
The alpha-fetoprotein test is considered to be extremely important for women who have a high risk of giving birth to children with congenital disabilities. This includes:
- Women who are of advanced age, meaning they are 35 or older
- Women with a family history
- Who have diabetes
- Who have high blood pressure
- Who have used harmful drugs or medications during their current or past pregnancies
In people who are not pregnant, the alpha-fetoprotein test can be used to diagnose and monitor many types of liver conditions, including: (8)
- Liver cancer
The test can also be used for detecting other cancers such as: (9)
Are There Any Risks Of The Alpha-Fetoprotein Test?
There are minor risks associated with the alpha-fetoprotein blood test. You will simply feel a slight pinch while your blood is drawn. Afterward, you may feel some pain at the injection site, or you may feel slightly faint. There is a minimal chance of excessive bleeding or a hematoma, which usually occurs when blood starts accumulating under the skin. There is also a minimal risk of the puncture site getting infected.
How Is The Alpha-Fetoprotein Test Done?
Your blood will be drawn for the alpha-fetoprotein test. This is a small outpatient procedure that is performed at a diagnostic lab. The process will only take a few minutes and is usually painless. There is no need for any special preparations before giving blood for this test.
A nurse will use a small needle to take blood from a vein, usually in the arm or hand. A specialist will then analyze the blood sample, and results will become available within a week or two.
Understanding the Alpha-Fetoprotein Test Results
In women who are not pregnant, the normal level of the alpha-fetoprotein in the bloodstream is generally less than 10 nanograms per milliliter of blood. If your level is unusually high and you are not pregnant, then it is usually an indication of liver diseases or certain types of cancers.
If you are pregnant and you have a higher than normal levels of alpha-fetoprotein, it may indicate a neural tube defect in the developing fetus. (10) However, one of the most common causes of getting elevated levels of alpha-fetoprotein is because of an inaccurate calculation or dating of the pregnancy. The levels of this protein tend to vary widely during the pregnancy, and the test will prove to be inaccurate if you have been pregnant for a longer or shorter period of the time than what you initially believed. (11)
If you are pregnant and the result of the alpha-fetoprotein test is too low, then it can indicate that the fetus has a chromosomal abnormality such as Edward’s syndrome or Down syndrome. (12, 13)
Another reason for getting abnormal alpha-fetoprotein levels could be due to a multiple pregnancy, meaning you are pregnant with twins or triplets. In some cases, an abnormal alpha-fetoprotein reading could also indicate a fetal death. (14)
According to data from the American Pregnancy Association, results of an alpha-fetoprotein test is considered to be abnormal for nearly 25 to 50 pregnant women out of every 1,000 expecting women who have been tested. However, only 1 in 16 and 1 in 33 women with abnormal results actually go on to deliver a baby with a congenital disability. (15)
If you get back abnormal test results, there is no need to panic. It does not automatically mean that your baby will be born with a birth defect. It only indicates that there is a need to undergo more tests to make a firm diagnosis. Your doctor is likely to perform another alpha-fetoprotein test along with an ultrasound to see images of the unborn child and to first also calculate the gestational age correctly.
Another invasive test, amniocentesis, may be recommended if the second test result also comes back abnormal. In amniocentesis, the doctor uses a needle to take out a tiny amount of amniotic fluid from around the fetus to check for any potential congenital disabilities. (16, 17)
Alpha-fetoprotein test is a prenatal test used commonly to rule out any birth defects in a developing baby. This blood test is also used in people who are not pregnant to check for cancer or liver disorders. Having abnormal levels of alpha-fetoprotein does not always indicate cancer, and neither does it mean that your child has a congenital disability. It only suggests that more testing is required to arrive at a confirmed diagnosis.
- Lau, H.L. and Linkins, S.E., 1976. Alpha-fetoprotein. American journal of obstetrics and gynecology, 124(5), pp.533-554.
- Cuckle, H., Wald, N. and Lindenbaum, R., 1984. Maternal serum alpha-fetoprotein measurement: a screening test for Down syndrome. The Lancet, 323(8383), pp.926-929.
- Dugoff, L., Hobbins, J.C., Malone, F.D., Vidaver, J., Sullivan, L., Canick, J.A., Lambert-Messerlian, G.M., Porter, T.F., Luthy, D.A., Comstock, C.H. and Saade, G., 2005. Quad screen as a predictor of adverse pregnancy outcome. Obstetrics & Gynecology, 106(2), pp.260-267.
- Renier, M.A., Vereecken, A., Van Herck, E., Straetmans, D., Ramaekers, P. and Buytaert, P., 1998. Second trimester maternal dimeric inhibin-A in the multiple-marker screening test for Down’s syndrome. Human reproduction (Oxford, England), 13(3), pp.744-748.
- Falah, N., Torday, J., Quinney, S.K. and Haas, D.M., 2015. Estriol review: clinical applications and potential biomedical importance. Clin Res Trials, 1(2), pp.29-33.
- Driscoll, D.A. and Gross, S.J., 2009. Screening for fetal aneuploidy and neural tube defects. Genetics in Medicine, 11(11), pp.818-821.
- Driscoll, D.A., Morgan, M.A. and Schulkin, J., 2009. Screening for Down syndrome: changing practice of obstetricians. American journal of obstetrics and gynecology, 200(4), pp.459-e1.
- Waldmann, T.A. and McIntire, K.R., 1974. The use of a radioimmunoassay for alpha‐fetoprotein in the diagnosis of malignancy. Cancer, 34(S8), pp.1510-1515.
- Abelev, G.I., 1971. Alpha-fetoprotein in ontogenesis and its association with malignant tumors. In Advances in cancer research (Vol. 14, pp. 295-358). Academic Press.
- Milunsky, A., Alpert, E., Kitzmiller, J.L., Younger, M.D. and Neff, R.K., 1982. Prenatal diagnosis of neural tube defects: VIII. The importance of serum alpha-fetoprotein screening in diabetic pregnant women. American journal of obstetrics and gynecology, 142(8), pp.1030-1032.
- Schnittger, A. and Selbing, A., 1984. Inaccurate gestational dating and maternal serum alpha‐fetoprotein screening. Acta Obstetricia et Gynecologica Scandinavica, 63(S119), pp.43-47.
- Barkai, G., Goldman, B., Ries, L., Chaki, R., Zer, T. and Cuckle, H., 1993. Expanding multiple marker screening for Down’s syndrome to include Edward’s syndrome. Prenatal diagnosis, 13(9), pp.843-850.
- DiMaio, M.S., Baumgarten, A., Greenstein, R.M., Saal, H.M. and Mahoney, M.J., 1987. Screening for fetal Down’s syndrome in pregnancy by measuring maternal serum alpha-fetoprotein levels. New England Journal of Medicine, 317(6), pp.342-346.
- Waller, D.K., Lustig, L.S., Cunningham, G.C., Golbus, M.S. and Hook, E.B., 1991. Second-trimester maternal serum alpha-fetoprotein levels and the risk of subsequent fetal death. New England Journal of Medicine, 325(1), pp.6-10.
- American Pregnancy Association. (2020). Maternal Serum Alpha-Fetoprotein Screening. [online] Available at: http://americanpregnancy.org/prenatal-testing/maternal-serum-alpha-fetoprotein-screening/ [Accessed 1 Mar. 2020].
- Drugan, A.R.I.E., Syner, F.N., Greb, A.N.N.E. and Evans, M.I., 1988. Amniotic fluid alpha-fetoprotein and acetylcholinesterase in early genetic amniocentesis. Obstetrics and gynecology, 72(1), pp.35-38.
- Lindfors, K.K., Gorczyca, D.P., Hanson, F.W., Tennant, F.R., McGahan, J.P. and Peterson, A.G., 1991. The roles of ultrasonography and amniocentesis in evaluation of elevated maternal serum α-fetoprotein. American journal of obstetrics and gynecology, 164(6), pp.1571-1576