AFP Testing (Triple Test)
The AFP test is the first screening test that many parents have in pregnancy.
The triple test (also commonly known as AFP or quad screen) is a maternal blood-screening test that looks for three specific substances: AFP, hCG, and Estriol. It is performed between the 15th and 17th week of pregnancy. Accurate results can still be obtained through 20 weeks gestation; in rare cases it may be performed up to 22 weeks. All pregnant women should be offered this screen, however it is particularly recommended for those over 35 years old. For detailed information about this test, see AFP Plus (from the American Pregnancy Association).
Sometimes a mother's AFP or quad screen test comes back as high risk for Trisomy 18. It is important to note that this is not a diagnosis, but a risk because this is a screening test. See How Trisomy 18 is diagnosed for an explanation of the difference between screening and diagnostic tests.
Because this is a screening test, only about 11% of those who receive a positive result for Trisomy 18 in the screen will actually have a pregnancy affected by Trisomy 18 (see Information on Accuracy of Maternal Serum Screening Test for more information).
If you have received a screening result indicating a higher-than-normal risk for Trisomy 18, what is your next step?
Typically a Level 2 ultrasound (also called a targeted ultrasound) is scheduled. A perinatologist or someone else who specializes in high-risk pregnancies usually performs the level 2 ultrasound. They are specially trained to look for the markers of Trisomy 18. See Level 2 ultrasound for more information about this test. Sometimes an amnio is also recommended at the same time as the ultrasound.