by EBSCO Medical Review Board
(CVS—Transcervical; Chorionic Villi Sampling—Transcervical)


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
Nine Week Old Fetus in Utero
Copyright © Nucleus Medical Media, Inc.

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

Possible Complications

Problems are rare, but there are some risks with this test. The doctor will go over some problems that could happen, such as:

  • Infection
  • Miscarriage
  • 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:

What to Expect

Prior to Test

Your doctor may meet with you to talk about:

  • 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

Description of Test

The vagina and cervix will be cleansed. A device called a speculum will be inserted to widen the opening of the vagina. An ultrasound will be used to guide a long, thin needle through the vagina to the uterus and placenta. This may cause some cramping. The needle will be used to take a tissue sample from the placenta. The needle will be removed. 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.

Post-procedure Care

At the Care Center

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.

At Home

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 

American Pregnancy Association 


Canadian Women's Health Network 

The Society of Obstetricians and Gynaecologists of Canada 


Chorionic villus sampling (CVS). American Pregnancy Association website. Available at: Accessed July 27, 2020.

Routine prenatal care. EBSCO DynaMed website. Available at: . Updated January 21, 2020. Accessed July 27, 2020.

Sampling of chorionic villus. EBSCO DynaMed website. Available at: . Accessed July 27, 2020.

Revision Information