Alpha-Fetoprotein (Amniotic Fluid)
Does this test have other names?
Amniotic fluid alpha-fetoprotein, AFAFP test
What is this test?
This test checks a sample of amniotic fluid to confirm a suspected birth defect called an open neural tube defect in your fetus. Spina bifida is an example of a neural tube defect.
Amniotic fluid is the liquid that protects and nourishes your fetus during pregnancy. When a developing baby has open neural tube defect, it often causes a high level of alpha-fetoprotein (AFP).
Why do I need this test?
You may have this test if you had an abnormal result from a blood test. You may also have had an ultrasound that showed the possibility of this defect. This test helps confirm whether the fetus does have a birth defect.
What other tests might I have along with this test?
Your doctor may also order another test called amniotic fluid acetylcholinesterase (AChE) to help find a neural tube defect. AChE is an enzyme found in blood, muscle, and nerve tissue.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
High levels of both AFP and AChE mean your fetus has an open neural tube defect. These tests have a 96 percent accuracy rate.
How is this test done?
This test requires a sample of amniotic fluid. The sample is collected during a procedure called amniocentesis. It is usually done in a medical office.
In this procedure you lie down on an examination table, and a health care professional uses an ultrasound machine project an image of your unborn baby onto a monitor. These images pinpoint where to draw the fluid sample without touching the fetus.
A health care provider applies local anesthetic to your abdomen then injects a needle to draw out a small sample of amniotic fluid. Collecting the sample of fluid usually only takes about five minutes, but you may be at the facility for 45 minutes or longer.
Does this test pose any risks?
Amniocentesis is considered a safe procedure, but you have a one in 300 to 500 chance that you may miscarry. Miscarriages can happen if you develop an infection in your uterus, if your water breaks prematurely, or if you go into early labor.
It's extremely rare for the baby to come into contact with the needle. The health care providers watch the monitor very closely.
After the procedure, you may feel cramping, leak a little fluid or blood from your vagina, or feel discomfort around the puncture site. If any of these symptoms persist or get worse, or if you develop a fever, call your health care provider right away. Ask your doctor if you should avoid certain activities after the procedure.
What might affect my test results?
Other factors aren't likely to affect your results.
How do I get ready for this test?
You don't need to prepare for this test. But be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.
- Fraser, Marianne, MSN, RN
- Marcellin, Lindsey, MD, MPH