Reasons, Preparations & Procedure For Conducting a Alpha-Fetoprotein (AFP) Test

Submitted on March 27, 2012

What is a Alpha-Fetoprotein Test?

The alpha fetoprotein AFP test is a prenatal test that is conducted in the second trimester of pregnancy and is used to check for any birth defects in the fetus. The AFP prenatal test checks the level of a naturally occurring substance in the amniotic fluid or the mother's blood for alpha fetoprotein. The role of this protein is to act as a substitute for serum albumin in a growing fetus. Serum albumin is a substance in the blood that allows lipophilic compounds to be transported in the blood, which is largely water based.

AFP test results are used to decipher whether there are any possible birth defects to look out for like neural tube defects and Down's syndrome. Usually, an AFP test with a false positive is also possible. This can occur due to individual differences in serum AFP of the mother. Typically, the amount of AFP gradually decreases after the second trimester onwards though some trace amounts will remain in the body forever but serving no real function. Some individuals will have high amounts in their blood normally and therefore a test must be confirmed after analyzing the amniotic fluid.

Why is it done?

An AFP test is one of those tests that are part of the screening of a fetus during the second trimester of pregnancy. It is used to test for birth defects like open omphalocele, neural tube defects - showing increase AFP levels, and Down's syndrome - showing decreased AFP levels.

How to prepare for the test?

There are no special preparations that you need to take when going in for an AFP test except to take all the doctors reports that you have accumulated so far and any special information. However, if the AFP test is going to be conducted on amniotic fluid, then you might have to let your doctor know if you have just eaten before the procedure or if you are on any hypertensive medication since anesthesia will be used during this time.

How is it done?

AFP tests can be done by taking a sample of the mother's blood for serum AFP level checks or it may also be done by checking the amniotic fluid. This procedure will require a local anesthetic in most cases. The procedure involves making a small hole in the abdomen and guiding an ultrasound guided probe into the uterus and finally the amniotic sac. From here, a small amount of amniotic fluid is then extracted. The extract contains fetal cells that can then be checked for any deformities. In addition to this, tests are also conducted for AFP levels.