Enhanced Alpha
Fetoprotein Test ("Triple Screen")
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What is the
test?
This blood test for pregnant women, often called
a “triple screen,” checks the levels
of protein and hormones being produced by the
fetus. The levels of three different substances
together can enable doctors to identify pregnancies
that are at a higher risk for birth defects such
as Down syndrome or neural tube defects (brain
and spinal cord problems). If the blood test
suggests problems, your doctor might recommend
additional tests, such as amniocentesis or fetal
ultrasound, to confirm the findings.
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How
do I prepare for the test?
Before having this test done, you need to think
carefully about what you would do with the results
once you have them. The results of this blood
test cannot show for sure whether you have either
a healthy fetus or one with a problem; it can
only suggest which patients might want to go
ahead with further testing. Because amniocentesis
(the test that is usually recommended after an
abnormal triple screen) has a small risk of miscarriage,
and because most people with an abnormal triple
screen decide to go ahead with amniocentesis,
this is an important decision. You should have
this test done only if you think the information
it offers would help you to make decisions about
your pregnancy.
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What
happens when the test is performed?
Your blood is drawn for this test sometime between
your 15th and 20th weeks of pregnancy. The blood
is tested for three protein and hormone levels:
maternal serum alpha fetoprotein (MSAFP), unconjugated
estriol (uE3), and human chorionic gonadotropin
(hCG). Your doctor needs to weigh you on the
day you have your blood drawn and ask when your
last period began or what your expected due date
is. The analysis of the results will take into
account your weight and stage of pregnancy to
determine whether the levels are normal.
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What
risks are there from the test?
There are no risks from this test itself, but
there are some risks from tests that might be
recommended if the test result comes back abnormal
(see "Amniocentesis,” page 3). This
test can be stressful for expectant parents.
Several things can cause the test to come back
as abnormal even when there are no real health
problems. Confusing results can happen, for example,
in twin pregnancies and when mistakes have been
made in estimating the age of the pregnancy.
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Must
I do anything special after the test is over?
No.
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How
long is it before the result of the test is
known?
The test results are available to your doctor
within two or three days.
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