What is the triple or quad screening?
The triple screening measures
the amounts of three substances in a pregnant woman's blood: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and estriol (uE3). When a test for the hormone inhibin A is added, it's called a
quad screening. These tests are also called the maternal serum triple or quad test, the
expanded AFP test, the AFP plus test, or the multiple marker screening test.
The amounts of these substances help your doctor find out the chance that
your baby has certain birth defects, such as
spina bifida, or
anencephaly. These tests can't show for sure that your baby has a birth defect. You would need a diagnostic test called amniocentesis to find out for sure if there is a problem.
The triple or quad screening is usually done at 15
to 20 weeks of pregnancy.
Each substance tested in a triple or
quad screening gives you different information about possible problems.
Together, these results give the best information. These screening tests look for the amount of:
Your doctor will look at the levels of these substances-along with your age and other factors-to see if your baby has a higher-than-average chance of having a birth defect.
How is it done?
A simple blood test is all that's needed for these tests.
The health professional taking a sample of your blood will:
- Wrap an elastic band around your upper arm. This makes the veins below the band larger so it is easier to put a needle into the vein.
- Clean the needle site with alcohol.
- Put the needle into the vein.
- Attach a tube to the needle to fill it with blood.
- Remove the band from your arm when enough blood is collected.
- Put a gauze pad or cotton ball over the needle site as the needle is removed.
- Put pressure on the site and then put on a bandage.
How accurate is it?
A screening test shows the chance that a baby has a certain birth defect. The accuracy of a screening test is based on how often the test correctly finds a birth defect.
- The triple and quad tests correctly find neural tube defects, such as
spina bifida, in 80 out of 100 fetuses who have it and find anencephaly in about 90 out of 100 fetuses.1 The tests miss spina bifida in 20 out of 100 fetuses who have it and miss anencephaly in 10 out of 100 fetuses.
- The triple test correctly finds
Down syndrome in 69 out of 100 fetuses who have it. It misses the condition in 31 out of 100 fetuses.2
- The quad test correctly finds
Down syndrome in 81 out of 100 fetuses who have it. It misses Down syndrome in 19 out of 100 fetuses.2