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The
Ultrascreen Test
What
is an Ultrascreen?
An Ultrascreen is a combination of two prenatal tests: a specialized ultrasound
measurement and two blood tests performed by fingerstick on the mother-to-be.
The information from the exam and blood work establishes your statistical
risk for that particular pregnancy being complicated with Down's Syndrome
and certain other chromosomal abnormalities. The results do not provide
positive diagnosis for these defects. They only determine your statistical
risk, and to indicate whether further, more invasive testing is warranted.
What
are the specific tests that make up the Ultrascreen?
Your
blood will be screened for the amount of two proteins: freeBeta-hCG and
PAPP-A. These proteins are found in the blood of all pregnant women.
The
ultrasound exam will reveal the baby's heartbeat, and determine gestational
age. We then take an accurate and sensitive measurement of the amount
of fluid behind the neck of the baby, called nuchal translucency (NT).
The results of the NT measurement and the blood samples are sent to a
highly specialized lab for evaluation and calculation of risk.
How
accurate is this type of first trimester screening?
The
combination of freeBeta / PAPP-A / nuchal translucency (the Ultrascreen
test) detects over 90% of Down's Syndrome and Trisomy 18 between 10 and
13 weeks. These reports do not completely eliminate the possibility that
the fetus may have birth defects, mental retardation, Down's Syndrome,
Trisomy 18, other chromosome abnormalities, or other disorders not detectable
by these screening tests. This screening will not detect neural tube defects
and other anomalies that my be detected by the triple screen test done
later, but second trimester ultrasound will detect these abnormalities
as least as often as blood tests.
Do
I have to do both ultrasound and blood tests?
Both
the blood screening and the ultrasound exam are offered separately. The
best detection rate is possible, however, when they are used together.
The nuchal translucency test (ultrasound measurement of NT alone) provides
an 80% detection rate for Down's Syndrome. When you add the blood test,
detection rate is greater than 90%.
Who
is a candidate for first trimester screening?
All pregnant women who are less than 35 years old, between 10 and 13 weeks
of pregnancy, and who have no other high risk for chromosomal abnormalities
are candidates for screening.
Certain
women over 35 may choose to undergo this genetic screening, in order to
avoid more invasive testing, but these women are offered definitive testing
(amniocentesis or CVS) without this screening if desired.
What
if my test shows an increased risk?
An increased risk does not mean a genetic disorder has been diagnosed.
Follow up tests such as amniocentesis and chorionic villus sampling are
then offered, which very accurately diagnose your baby's chromosomal make-up.
You may need to read more about these follow-up tests to decide if prenatal
genetic screening is right for you.
You
may wish to visit the GeneCare
Laboratory for more information on the Ultrascreen test.
(Genecare
is our reference laboratory, and only one of a select few who are certified
to run this test in the United States)
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