Chorionic villus sampling is a test that is done to look for chromosomal abnormalities in the baby. It is done during the 9th to 13th weeks of pregnancy.
A sample of tissue from the placenta is removed for testing. This is the organ that provides nutrients and oxygen to the baby. It also removes waste from the baby’s blood.
|9 Week Old Fetus in Utero|
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Reasons for Test
This test is done to find out if the baby has a chromosomal abnormality, like Down syndrome. It can also look for problems with the genes, such as cystic fibrosis.
This test may be done when:
- Other tests, such as a first trimester ultrasound or blood tests have abnormal results
- A prior pregnancy had a chromosomal abnormality
- The mother is 35 years old or older
- The mother or partner is a carrier of a genetic problem
- There is a family history of a genetic problem
Problems are rare, but there are some risks with this test. The doctor will go over some problems that could happen, such as:
- Rh incompatibility—a sensitivity to the baby's blood, which may enter the mother's bloodstream
- The need to repeat the test, such as if not enough cells were taken
Things that may raise the risk of problems are:
- Having an active infection, such as a sexually transmitted infection
- Carrying more than 1 baby
- Bleeding from the vagina during pregnancy
What to Expect
Prior to Test
Your doctor may meet with you to talk about:
- Anesthesia options
- Any allergies you may have
- Whether you need to have a full bladder before the test and the amount of fluids you need to drink
- Arranging for a ride to and from the test
You may be given a local anesthesia. The skin will be numbed.
Description of Test
An ultrasound will be used to guide a long, thin needle through the abdominal wall. The needle will enter the uterus and placenta, avoiding the baby. This may cause some cramping. The needle will be used to take a tissue sample from the placenta. The needle will be removed. A bandage will be placed over the area. The sample will be sent to a lab for testing.
How Long Will It Take?
30 to 45 minutes
Will It Hurt?
You may have some cramping and spotting right after the test. It should go away in a couple of hours.
The baby's heart rate and vital signs will be monitored. A woman with Rh negative blood will need to receive Rhogam to prevent a health problem called isoimmunization.
Rest will be needed in the first 24 hours before going back to activities. The health team will call with the test results.
Call Your Doctor
Call the doctor if you are not getting better or you have:
- Signs of infection, such as fever and chills
- Blood or fluid leaking from the vagina
- Belly contractions
- New or worsening symptoms
If you think you have an emergency, call for medical help right away.
American Congress of Obstetricians and Gynecologists http://www.acog.org
American Pregnancy Association http://www.americanpregnancy.org
Canadian Women's Health Network http://www.cwhn.ca
The Society of Obstetricians and Gynaecologists of Canada http://www.sogc.org
Chorionic villus sampling (CVS). American Pregnancy Association website. Available at: https://americanpregnancy.org/prenatal-testing/chorionic-villus-sampling/. Accessed July 27, 2020.
Routine prenatal care. EBSCO DynaMed website. Available at: https://www.dynamed.com/management/routine-prenatal-care-36 . Updated January 21, 2020. Accessed July 27, 2020.
Sampling of chorionic villus. EBSCO DynaMed website. Available at: https://www.dynamed.com/lab-monograph/sampling-of-chorionic-villus . Accessed July 27, 2020.
- Reviewer: EBSCO Medical Review Board Elliot M. Levine, MD, FACOG
- Review Date: 03/2020
- Update Date: 03/12/2021