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Chorionic villus sampling (CVS) is a test that can find certain problems with your
fetus. These include many diseases that run in families (genetic disorders) and chromosome defects. It is done during early
often between the 10th and 12th weeks.
are tiny finger-shaped growths found in the
placenta. The chorionic villus
cells have the same genetic material as the baby's cells. During CVS, a sample of the
chorionic villus cells is taken. The sample is collected by putting a thin tube (catheter) through the
vagina or by putting a
long, thin needle through the belly.
Ultrasound is used to guide the catheter or needle
to the right spot.
CVS can find many genetic disorders,
Tay-Sachs disease and
hemophilia. It can also find chromosome defects, such as
Down syndrome. CVS can't find
neural tube defects.
CVS is done
earlier in pregnancy than
amniocentesis (usually done at 15 to 20 weeks). And the results of CVS are available sooner. This
gives you more time to make decisions about your pregnancy or plan for the future.
Health Tools help you make wise health decisions or take action to improve your health.
may be done during your first trimester of pregnancy
to find certain birth defects.
You may choose to have this test because:
You may be asked to drink a glass of
fluid about an hour before the test. This is so your bladder will be full. A full
bladder makes it easier to do the test.
You will be asked to sign a consent form that says you understand the risks of the test and agree to have it done.
Be sure to tell your doctor before the procedure if you are
allergic to any medicines, such as numbing medicines (local anesthetics).
Talk to your doctor if you have any concerns
about the need for the test, its risks, how it will be done, or
what the results will mean. To help you understand the importance of this test,
fill out the
medical test information form(What is a PDF document?).
CVS is usually done by a
perinatologist. It may be done in the doctor's office or the hospital.
An overnight stay in the hospital usually is not needed.
CVS may be done either through the belly (transabdominal) or through the
cervix (transcervical). The choice may
depend on the position of the fetus and the placenta.
You will lie
on your back on an exam table with your belly bare.
Ultrasound will be used to
help your doctor guide the needle to the placenta. Gel will be rubbed on your belly. An ultrasound
device (transducer) will be moved over
your belly. It gives off and picks up sound waves. The sound waves are sent to a computer to make a picture
uterus, your baby, and the placenta on a screen.
The doctor can also use ultrasound to check your baby's heart rate. For more information, see the topic
Your skin where the
needle will be put in is cleaned with alcohol and numbed with a medicine. Your
doctor then puts a long, thin needle through your belly and uterus to the
placenta. The needle is used to collect a sample of the chorionic villus cells.
After the sample is collected, the doctor may listen to your baby's heart and check your blood pressure, pulse, and breathing.
You will take off your clothes below the waist. You will have a paper or cloth covering around your waist. You will lie on your back on an exam table with your feet
raised and supported by stirrups.
Your doctor will put a special tool with curved sides
(speculum) into your vagina. The speculum gently spreads apart the vaginal
walls. This lets the doctor see the inside of the vagina and the cervix. The cervix
will be cleaned with a special soap.
Your doctor will use ultrasound to guide a thin tube (catheter) through your cervix to the placenta. Gel will be rubbed on your belly. An
ultrasound device (transducer) will be moved over your belly. It gives off and picks up sound waves. The sound waves are sent to a computer to
make a picture of your uterus, your baby, and the placenta. The doctor can also use ultrasound to check your
baby's heart rate.
For more information, see the topic
When the catheter is
in the right place, a sample of chorionic villus cells will be collected.
After the sample is collected, the doctor may listen to your baby's heart
and check your blood pressure, pulse, and breathing.
You will feel a short, sharp sting from the needle used to give the
numbing medicine. There is usually no pain when the collecting needle is put in
the belly. You may have some cramping when the needle is in your
Most women do not find this procedure
painful. It may feel like having a Pap
test or pelvic exam. You may have some cramping when the catheter is
put through your cervix.
CVS may cause
cramping, leakage of amniotic fluid, and vaginal spotting. These will go away in 1
to 2 days. If you had
the belly procedure, you may feel some soreness where the needle was put in.
CVS also increases the risk of:
There is a very small chance that CVS could cause bleeding that could let your blood mix with your baby's blood. If you
Rh-negative blood, you will be given the Rh immunoglobulin vaccine (such as RhoGAM). This can prevent Rh sensitization, which could harm
your baby if he or she has Rh-positive blood.
It is normal to have mild
cramping and vaginal spotting and to leak a little amniotic fluid for
the first day or two after the procedure.
Call your doctor right away if you
Chorionic villus sampling (CVS)
is a test that can find certain problems with your
fetus. It is done during early
often between the 10th and 12th weeks.
material (chromosomes) of the cell sample is
looked at carefully. Normally
there are 46 chromosomes in each cell, arranged in 23 pairs. The number and arrangement of the chromosomes in the sample can show if your baby has a genetic disease. Chromosomes also
show the sex of your baby.
It may take 1 to 2 weeks to get CVS results.
No abnormalities are found in
the genetic material of the chorionic villus cells.
Abnormalities are found in the
genetic material of the chorionic villus cells.
Your doctor will talk with you
about anything that might keep you from having the test or that may change the
Caughey AB, et al. (2006). Chorionic villus sampling compared with amniocentesis and the difference in the rate of pregnancy loss. Obstetrics and Gynecology, 108(3): 612–616.
Other Works Consulted
American College of Obstetricians and Gynecologists (2007, reaffirmed 2008). Screening for fetal chromosomal abnormalities. ACOG Practice Bulletin No. 77. Obstetrics and Gynecology, 109(1): 217–227.
Cunningham FG, et al. (2010). Prenatal diagnosis and fetal therapy. In Williams Obstetrics, 23rd ed., pp. 287–311. New York: McGraw-Hill Medical.
Wapner RJ, et al. (2009). Prenatal diagnosis of congenital disorders. In RK Creasy et al., eds., Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice, 6th ed., pp. 221–274. Philadelphia: Saunders Elsevier.
ByHealthwise StaffPrimary Medical ReviewerSarah Marshall, MD - Family MedicineSpecialist Medical ReviewerSiobhan M. Dolan, MD, MPH - Reproductive Genetics
Current as ofMay 22, 2015
Current as of:
May 22, 2015
Sarah Marshall, MD - Family Medicine
& Siobhan M. Dolan, MD, MPH - Reproductive Genetics
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