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(CVS—Transcervical; Chorionic Villi Sampling—Transcervical)


Chorionic villus sampling is a test that is done during early pregnancy to test for chromosomal problems in the fetus. It involves removing a few of the chorionic villi which make up most of the placenta. The placenta is the organ that provides nutrients and oxygen to the baby during pregnancy. It also removes waste from the baby’s blood. The test is done during the 9th-13th weeks of pregnancy.

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

Reasons for Test

Chorionic villi contains valuable information about the baby’s genes. By testing chorionic villi, the doctor can find out if the baby has a chromosomal abnormality, like Down syndrome . The test can also detect genetic disorders, like cystic fibrosis . It cannot detect neural tube defects, such as spina bifida .

This test may be considered when:

  • Other tests, such as a first trimester ultrasound reveal abnormal results
  • A prior pregnancy had a chromosomal abnormality
  • The mother is 35 years old or older
  • You or your partner is a carrier for a genetic disorder
  • There is a family history of a genetic disorder

When the results of the testing are available, you will need to consider what you will do with the information. If there is a genetic disorder, further counseling can be helpful. Your doctor can help you understand the pros and cons of having this test, as well as talk about your options after you know the results.

Possible Complications

There are some risks with having this test, such as:

  • Miscarriage
  • Cramping
  • Bleeding from the vagina
  • Sensitivity to your baby’s blood, which may enter your bloodstream, also called Rh incompatibility
  • Infection in the uterus

Chorionic villus sampling through the cervix may not be advised if you:

What to Expect

Prior to Test

Since you may need to have a full bladder, drink plenty of fluids before the test. However, depending on how your placenta is positioned, you may be asked to urinate before the test. Talk with your doctor about specific ways to prepare for the test. Also, arrange to have someone drive you home from the hospital.

Description of Test

An ultrasound will be used to find the position of your placenta and take measurements to determine the age of the fetus. An ultrasound uses sound waves to create images of structures inside the body.

The ultrasound images will be used as a guide to take a tissue sample from your placenta. First, your vagina and cervix will be cleansed with antiseptic. Next, a device called a speculum will be inserted to widen the opening of the vagina. A thin, hollow tube will be inserted through your vagina and cervix. When it reaches the placenta, it will gently suction a small tissue sample. You may feel cramping while the sample is being taken.

After Test

Your baby's heart rate may be monitored using an ultrasound. You will be encouraged to rest when you are home. You will most likely be able to return to normal activities the next day. If you have a RH negative blood type, you will need to receive Rhogam to prevent a condition called isoimmunization.

How Long Will It Take?

30-45 minutes

Will It Hurt?

You may feel some cramping during and after the test. You may also have a small amount of bleeding right after the test.


It may take 1-2 weeks to receive your test results. You will go over the results with your doctor or a genetic counselor.

If the test results are unclear, you may need to have another test, called an amniocentesis to give you a better understanding of the results.

If the results show that your baby has a genetic disorder or chromosomal problems, you and your doctor will discuss how to manage your pregnancy. This may be a stressful time. Get support from your family, friends, and healthcare team.

Call Your Doctor

It is important to monitor your recovery. Alert your doctor to any problems. If any of the following occur, call your doctor:

  • Increased or heavy bleeding from your vagina
  • Leaking of amniotic fluid
  • Uterine contractions
  • Fever
  • Chills

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: http://www.americanpregnancy.org/prenataltesting/cvs.html. Updated September 2, 2016. Accessed March 9, 2018.

Routine prenatal care. EBSCO DynaMed website. Available at:  https://www.dynamed.com/topics/dmp~AN~T114252/Routine-prenatal-care  . Updated March 17, 2017. Accessed March 9, 2018.

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