Prenatal Test: Multiple Marker Test
What Is the Multiple Marker Test?
The multiple marker test is a blood test offered to all pregnant women. Doctors use it to screen for chromosomal disorders and neural tube defects.
Test results can be combined with first trimester screening tests to give more accurate results (this is called an integrated screening test).
It is important to remember that this is a screening test, not a diagnostic test. If the test shows there might be a problem, another test must be done to confirm or rule out a diagnosis.
Why Is the Multiple Marker Test Done?
The multiple marker test is done between weeks 15 and 20 of a woman's pregnancy to screen for neural tube defects (such as spina bifida) and chromosomal disorders (such as Down syndrome and trisomy 18).
Depending on the number of things measured, the test also is called:
- a "triple screen" or "triple marker" because it looks at the levels of a protein, alpha-fetoprotein (AFP), and two pregnancy hormones, estriol and human chorionic gonadotropin (hCG)
- a "quadruple screen" ("quad screen") or "quadruple marker" ("quad marker") when the level of another substance — inhibin-A — is also measured
This screening calculates a woman's individual risk based on the levels of the three (or more) substances, as well as:
- her age
- her weight
- her race
- whether she has diabetes requiring insulin treatment
- whether she is carrying one fetus or more than one
The greater number of markers increases the accuracy of the multiple marker test and better identifies the possibility of a problem. In some cases, doctors will combine the results of this test with results from the first trimester screen to get an even better idea of a baby's risk for Down syndrome and neural tube defects.
Should I Have the Multiple Marker Test?
All pregnant women are offered some form of this test. Some health care providers include more parts of it than others.
Remember that this is a screening test, not a diagnostic test. It's also not foolproof — a problem might not be detected, and some women with abnormal levels are found to be carrying a healthy baby. Further testing is recommended to confirm a positive result.
When Is the Multiple Marker Test Done?
The blood tests are typically done between 15 and 20 weeks.
What Happens During the Multiple Marker Test?
Blood is drawn from the mother.
When Are the Results Available?
Test results usually are ready within a week, but can take up to 2 weeks.