Triple or Quad Tests for Birth Defects
What is the triple or quad test?
The maternal blood triple and quad tests, also called the triple and quad screens, are a way to check for the risk of birth defects before a baby is born. The triple test measures the levels of 3 proteins and hormones during pregnancy from a sample of the mother's blood. The quad test measures 4 proteins and hormones. These tests are more accurate than having just the alpha-fetoprotein test alone to see if the baby could have a problem.
Substances that may be measured in these tests are:
- alpha-fetoprotein (AFP), a protein produced by the baby's liver
- human chorionic gonadotropin (hCG), a hormone produced by the placenta
- estriol (uE3), a hormone produced in the placenta and the liver of the baby
- dimeric inhibin-A (DIA), a protein made by the placenta
Why are these tests done?
Some of the birth defects that these tests may find are:
- Down syndrome or other chromosome (genetic) problems
- brain or spinal cord defects (also called neural tube defects), such as spina bifida (the spine has not closed normally) and anencephaly (all or part of the brain is missing)
- failure of your baby's abdomen to close, so that the intestines are held in a sac outside the abdomen
- a defect in the esophagus (food pipe)
- kidney problems
- severe skin problems
How are the tests done?
The tests are usually done between the 15th and 18th weeks of pregnancy. A small amount of blood is taken from your arm with a needle. The blood is collected in tubes and sent to a lab.
These blood tests may be done by some healthcare providers as part of a new test called the integrated test. The integrated test is done in 2 stages. The first stage is done when you are about 12 weeks pregnant. It includes an ultrasound of the baby to look at the thickness of the skin on the baby's neck and a test of the mother's blood called PAPP-A (pregnancy-associated plasma protein A). The second stage is another test of the mother's blood when at 15 to 16 weeks of pregnancy. These blood tests include the AFP, total hCG, uE3, and inhibin-A tests.
How will I get the test results?
Ask your healthcare provider when and how you will get the results of your test.
What do the test results mean?
The tests cannot tell for certain that there is a birth defect, but they can give an idea of the risk of certain birth defects. The lab figures the risk based on the levels of the 3 or 4 tested substances in the blood. Factors such as the age of the unborn baby; your age, weight, and race; and whether you take insulin to treat diabetes are also considered.
The tests are not 100% accurate. A baby could have a birth defect that is not found by the blood tests. However, if all the tests are normal, your chance of having a baby with a birth defect is very low.
What if my test results are not normal?
Up to 1 of every 10 women who have these blood screening tests have results that are not normal. An abnormal test result does not mean that a baby has a birth defect. In fact, most women with abnormal results have healthy, normal babies. A few reasons the results may appear to be abnormal may be that the due date is not correct or because you are pregnant with more than 1 baby, such as twins.
If the test results are not normal, you may have other follow-up tests, such as:
- Ultrasound exam, which helps determine the baby's age and can show if you are carrying more than 1 baby. It can also find some of the more obvious birth defects.
- Amniocentesis, which is a way to get cells from the baby that are in the amniotic fluid surrounding the baby. The cells can be studied to look for chromosome problems, such as Down syndrome. The level of AFP in the fluid may also be tested.
- Cordocentesis, or umbilical blood sampling, which is a way to get cells from the baby's blood that can be tested for chromosome problems.
Talk to your provider about your results and ask questions. Ask if and when you need more tests. If the results of these and follow-up tests show that your baby does have a problem, your provider will talk to you about your choices for treatment. The information can help you decide how to manage a pregnancy with a baby affected by the problem.
Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.
HIA File preg5308.htm Release 13/2010