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Common Prenatal Tests:
Chorionic Villus Sampling (CVS)
Many women undergo
tests during pregnancy to check for birth defects, genetic
disorders, and other problems. Find out more here about
Chorionic Villus Sampling (CVS).
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Why
do we get tested and Who Gets tested?
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| Between 10 and 12 weeks,
some women opt to have a prenatal test called CVS (Chorionic
Villus Sampling). CVS may be offered if the woman is over age
35, has a child or a previous pregnancy affected by a birth
defect, or if there is other family history of certain birth
defects. CVS is considered to be 98% accurate in the diagnosis
of chromosomal defects, such as Down Syndrome.
CVS carries a small risk of
miscarriage of 0.5% - 1.0%, according to the Centers for
Disease Control (CDC). Futher, the American Academy of Family
Physicians reports that some studies suggest that in a small
number of cases, CVS may cause defects in the infant's fingers
or toes if the test is done before 9 weeks of gestation.
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The
Actual Test
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| There are two ways to
complete this procedure: via the vagina and cervix (transcervical
CVS) or through the abdomen (transabdominal CVS). The
transcervical method is preferred unless you have a retroverted
uterus, in which case, transabdominal is safest. Local
anesthesia may be used in some cases.
You should have a full
bladder before going for the test. With the help of an
ultrasound to visualize the uterus and placenta, a thin needle
(through the abdomen) or narrow tube (though the cervix) takes
a small tissue sample from the chorionic villi, tiny pieces of
placental tissue that attach the pregnancy to the uterine wall.
The cells are then tested for chromosomal problems (processed
directly or cultured for chromosomal, DNA or biochemical
analysis), and results are usually back in about 10 days.
The March of Dimes reports
that according to a national study, one in five women
experience cramping following CVS; one in three women have some
bleeding or spotting, which ordinarily stops within a few days.
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