How To Prepare
You may be asked to drink a glass of
fluid about an hour before the test so that your bladder is 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.
Talk to your doctor about any concerns
you have regarding 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?).
Be sure to tell your doctor if you are
allergic to any medicines, such as numbing medicines (local anesthetics), before the procedure.
How It Is Done
Chorionic villus sampling is most
commonly done by a
perinatologist in the doctor's office or the hospital.
An overnight stay in the hospital usually is not needed unless problems occur
during the procedure.
Transabdominal (through the belly) chorionic villus
sampling or transcervical (through the
cervix ) chorionic villus sampling can be done. The choice may
depend on where the fetus and placenta are in the uterus.
Through the belly (transabdominal)
You will lie
on your back on an examination table with your belly bare.
Gel will be rubbed on your belly to use with the ultrasound unit. An ultrasound
device (transducer) that gives off and picks up sound waves will be passed over
your belly. The reflected sound waves are sent to a computer to make a picture
uterus, your baby, and the placenta on a screen.
Your doctor or an ultrasound technician will look at the picture on the screen
to help guide the needle used to collect a sample of the chorionic villus. Your
baby's heart rate can also be checked during the procedure using ultrasound.
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 and collects a sample of the chorionic villus cells.
After the sample is collected, your doctor may listen to your baby's heart rate
and check your blood pressure, pulse, and breathing.
Through the cervix (transcervical)
You will be
asked to take off your clothes below the waist and drape a covering around your
waist. You will then lie on your back on an examination table with your feet
raised and supported by stirrups. This allows your doctor to look at your
Your doctor will put an instrument with curved sides
(speculum) into your vagina. The speculum gently spreads apart the vaginal
walls, allowing the inside of the vagina and the cervix to be seen. The cervix
will be cleaned with a special soap.