What is a triple or quadruple screen test?
maternal serum triple screen, sometimes called the triple test or MSAFP+ test,
measures the amounts of three substances in a pregnant woman's blood:
human chorionic gonadotropin (hCG), and
estriol (uE3). The levels of these substances help
estimate the risk that a fetus may have certain defects. The test results are
computed based on a woman's age, her weight, her race, and how far along her
pregnancy is, among other factors.
The quadruple screen combines
the triple screen and a test for the
hormone inhibin A, which is produced by the fetus and
placenta. One large study of over 23,000 women has
reported that the quadruple screen detects almost 86% of all Down syndrome
cases. Based on this study, the quadruple test is more likely to pick up
Down syndrome and may be less likely to be
false-positive than the triple screen.1
The triple screen is only reliable when it is done between 15 and 20
weeks' gestation. This is why your doctor might use a fetal ultrasound to
confirm how many weeks pregnant you are.
The American College of
Obstetricians and Gynecologists recommends that all women be offered Down
syndrome screening, including the triple or quad screen.
What can the triple or quadruple screen test tell me?
The triple or quad screen estimates the risk that a fetus may have certain birth defects, including Down syndrome,
neural tube defects, and certain rare genetic
problems. For more information, see:
What do I do if I have a positive triple or quadruple serum screen test result?
Normal results tell you that there is no need
for further testing unless you have a separate concern, such as a known genetic
disease in your family. Positive results tell you that there is a greater than
average chance of a birth defect. But if the average risk for your age is very
low or your risk is above average but still very low, you may choose not to
have any additional diagnostic tests.
If your serum screen results suggest that your fetus might have a birth defect,
including Down syndrome or a neural tube defect, a fetal ultrasound will be
done as soon as possible. If your test results are abnormal, a fetal ultrasound
can confirm the fetal age and number of fetuses. (An incorrect fetal age or
pregnancy with twins or more can lead to a false-positive result.) An
ultrasound can also be up to 99% accurate in detecting cases of neural tube
defects.2 But ultrasound isn't a very dependable test
for signs of Down syndrome or for genetic diseases.
If your serum screen is positive and the fetal ultrasound shows no problems, you can have an amniocentesis to check for genetic problems.
Amniocentesis is accurate in helping diagnose genetic problems. For example,
the test is more than 99% accurate when used to diagnose Down syndrome.2 In most cases, the amniocentesis results are normal.
- If your serum screen is positive and the
fetal ultrasound suggests a possible genetic fetal problem, an amniocentesis
can be used to test for specific genetic markers and other substances in the
If a birth defect is found, you can learn what to expect
and make plans for having a child with Down syndrome or a birth defect, or you
can decide to terminate the pregnancy.
What are the risks of NOT having a triple or quadruple serum screen test?
The most common risk of having a triple or
quadruple screen test is unnecessary worry. Most women have normal serum screen
results. Of women who have positive results, most turn out to have no problems.
This tendency toward false-positive triple screen results increases as you age.
(The quadruple screen may be slightly less likely to give you a false-positive
If you don't have the triple or
quadruple screen or other diagnostic tests, you could potentially give birth to
a baby with an undiagnosed birth defect or Down syndrome.
- Such a birth can be more complicated and
risky for the baby when a doctor is not expecting newborn health
- You could give birth in a hospital that does not have a
neonatal intensive care unit (NICU) for sick newborns.
- A fetus
with a rare, severe defect sometimes dies before delivery.
advance knowledge, you might not be emotionally prepared for a Down syndrome or
For general information about the triple or quadruple
test, see the medical tests
Alpha-Fetoprotein in Blood,
Human Chorionic Gonadotropin (hCG),
Hormone Inhibin A.