| What is Second Screen™?
Second Screen is a blood test performed in the
second trimester of pregnancy that identifies
pregnancies at increased risk of having Down
syndrome, other
chromosome problems, or an open neural tube defect. The blood test analyzes
AFP (alpha-fetoprotein) and freeBeta™ (a component of hCG, the "pregnancy
hormone") which are proteins found in the blood of all pregnant women. Second
Screen™ measures the levels of MSAFP and freeBeta hCG between
14 - 22 week of gestation and estimates the risk for having a baby affected
with Down syndrome, open neural tube defects (ONTD's), and Trisomy 18.
What abnormalities can the Second Screen™ test
detect?
Down syndrome is one of several hundred types of chromosome disorders. Chromosomes
contain the genetic instructions which direct how the baby will develop. Chromosome
disorders occur when a baby receives too few or too many chromosomes by chance
at conception. Down syndrome occurs in about 1 in 800 live-born babies and
leads to mental retardation and other birth defects.
Trisomy 18 is a severe chromosome disorder which
causes profound mental retardation and multiple
birth defects. Like Down syndrome, the chance
to have a baby with Trisomy 18 increases with the
age of the parents.
An ONTD is a type of birth defect that occurs
when the developing baby's spine or skull does
not form completely. ONTD's are among the most
common serious types of birth defects. About 1
to 2 out of 1000 live born babies is born with
an ONTD.
How accurate is Second Screen™?
Second Screen has been documented to be the most accurate 2nd trimester
test available. MSAFP/freeBeta detects >95% of open neural tube defects
(ONTD's), MSAFP/freeBeta detects 80% of Down syndrome and 70% of Trisomy 18. These
reports do not eliminate the possibility the fetus may have birth defects,
mental retardation, or other disorders not detectable by these screening tests. Screening
will not detect all neural tube defects, chromosome abnormalities or pregnancies
with perinatal complications.
Both Second Screen and other trisomy profile
tests screen for the same abnormalities; however,
the Second Screen™ test detects a higher
percentage of cases of Down syndrome and open neural
tube defects. While the trisomy profile will detect
5 or 6 out of 10 cases of Down syndrome, the Second
Screen™ test can detect 7 or 8 out
of 10 cases of Down syndrome.
What if my test shows an increased risk?
An increased risk does not mean a chromosome disorder has been diagnosed. Your
doctor or genetic counselor will discuss additional testing which can determine
whether your baby has a disorder or if there are other explanations for this
test result. For example, you may be further along in the pregnancy than previously
thought, you may have twins, or the blood protein levels may be normal variations. It
may also mean the screening test has identified a baby with a disorder. Additional
testing including genetic counseling, ultrasound and amniocentesis for chromosome
and AFP testing can safely and accurately determine if your baby has one of
the screening disorders.
Who should consider having a Second Screen™ test?
Screening tests should be offered to all pregnant women who are less than 35. If
you are over age 34 or have an increased risk of a chromosome problem in your
baby, you can still have a screening test performed. However, it is still
recommended that you consider having a CVS (chorionic villi sampling) or amniocentesis
for prenatal chromosome testing performed.
How can I have a Second Screen™ test
performed?
This test may be ordered through your doctor, or you may request a self-collection
kit. The blood is collected using a fingerstick lancet, much like diabetic
blood testing is done. The sample is collected on a blood card which can be
easily mailed through the regular postal service using our mailer envelope. You
can collect the sample yourself, or take the card to your doctor for collection.
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