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decision pointShould I have chorionic villus sampling (CVS)?

Chorionic villus sampling (CVS) is a type of prenatal testing-a test done while a woman is pregnant to look for problems with the fetus. You may want to have CVS if the information it provides might change your plans.

Consider the following when making your decision:

  • CVS is done in the first trimester. If the test shows a serious problem, you have more time to prepare for the birth or a chance to end the pregnancy when it is safest and easiest. If the news is good, you have less time to worry.
  • CVS can find hundreds of diseases and defects, including Down syndrome. Finding out that your baby does not have one of these problems can be reassuring. But no test can rule out all problems or guarantee that your baby will be healthy.
  • CVS cannot detect a neural tube defect, such as spina bifida. If you are most concerned about neural tube defects, you may want to choose amniocentesis instead. Or you can have CVS and then a blood test later to find these problems.
  • CVS is not a routine test because it does carry a small risk of miscarriage. Out of 400 women who have CVS, from 1 to 4 of them will have a miscarriage. It is up to you to decide if the information you would get from the test is worth this risk.
  • CVS may be expensive. Most insurance companies will cover the cost for women older than 35. But if cost is an issue, you may decide to choose another type of testing.

What is chorionic villus sampling?

Chorionic villus sampling (CVS) is a test that can find certain problems with a fetus. CVS is done late in the first trimester, most often between the 10th and 12th weeks.

CVS can find:

  • Chromosomal birth defects, such as Down syndrome.
  • Hundreds of inherited diseases, such as Tay-Sachs disease and hemophilia.

CVS cannot find neural tube defects, such as spina bifida, so a blood test (alpha-fetoprotein test) is recommended along with it. This blood test is usually done between the 16th and 18th weeks of pregnancy.

Should I consider CVS?

CVS may be a good choice for you if:

  • You have had a screening test in the first trimester that suggests that your fetus may have Down syndrome. (This is an ultrasound of the fetus's neck [nuchal translucency] and a test of your blood.)
  • You are 35 or older. At 35, your risk of having a child with Down syndrome is high enough that you may want to think about testing, and the risk increases as you age. In mothers who are 35, about 1 baby in 350 is born with Down syndrome. By age 40, about 1 baby in 100 is born with Down syndrome.1
  • Either or both parents could pass on a disease that runs in the family (genetic disorder), such as Tay-Sachs disease or sickle cell disease, or a chromosome defect.
  • You have a medical reason to need to know whether the fetus is male or female. This is important when a parent is a carrier of a sex-specific disease, like hemophilia or Duchenne muscular dystrophy. Both of these diseases occur mainly in males.
  • You already have a child who has Down syndrome or another chromosome defect.
  • An ultrasound suggested that the fetus may have a birth defect.

CVS may be expensive, and it is not available in all areas. Most insurance companies will cover the cost for women older than 35. But if cost or availability is an issue, you may decide to choose another type of testing.

How is CVS done?

During CVS, a sample of chorionic villus cells is taken and checked for problems. Chorionic villi are tiny fingerlike growths in the placenta. The genetic material in these cells is the same as that in the fetus's cells.

The doctor can collect the sample in one of two ways:

  • Put a thin flexible tube (catheter) through the vagina and cervix into the placenta. This is called transcervical CVS.
  • Put a long, thin needle through the belly into the placenta. This is called transabdominal CVS. It is similar to the way amniocentesis is done.

The doctor uses ultrasound to guide the catheter or needle to the right spot.

How would I use the results from CVS?

Normal results from CVS suggest that a fetus does not have a chromosome or gene defect. This can be reassuring. But it is important to remember that no test can rule out all problems or guarantee that your baby will be healthy and free of birth defects.

If the test shows that your fetus has a disease or birth defect, you can make informed, if hard, decisions. Your choices will depend on many things. These include the type of defect involved and your feelings. For example, you may want to think about:

  • Whether to continue the pregnancy. If a fetus has a severe defect, some women choose to end the pregnancy, which is safest and easiest in the first trimester. Others use the time to learn about caring for and raising a child who has a birth defect or disease.
  • Where to have the baby. If the fetus has a serious problem, it is best to deliver at a hospital with a neonatal intensive care unit (NICU) that offers special care for newborns.
  • Whether to have a vaginal delivery or to plan a C-section, based on the fetus's problem.

What are the risks of CVS?

CVS increases the chance of:

  • Infection in the uterus.
  • Miscarriage. In one recent study of highly trained providers, about 1 woman in 400 who have CVS had a miscarriage.2 Some studies have shown a slightly higher risk, from 2 to 4 in 400.3 This greater risk may be more likely in medical centers with less experienced providers.

There is a very small chance of CVS causing bleeding, which could mix your blood and your fetus's blood. If you have Rh-negative blood, you will be given a vaccine before the test to prevent Rh sensitization.

What are the risks of not having CVS if it is recommended?

If you don't have CVS or other prenatal testing and the baby has a disease or birth defect:

  • The birth could be harder and more risky for the baby if the doctor doesn't know about the problem ahead of time.
  • You could give birth in a hospital that doesn't have a neonatal intensive care unit for sick newborns.
  • You may not be emotionally ready for a baby who is sick or has a birth defect.

Talk to your doctor about all of your testing options. You may be able to rule out a genetic condition with another type of test.

Is there another test I can have instead of CVS?

You could also consider amniocentesis, which is done in the second trimester. Amniocentesis can detect more than 100 inherited diseases and Down syndrome, as well as neural tube defects.

For this test, the doctor inserts a needle through your belly into the uterus and draws out a small amount of amniotic fluid. To look for genetic information, amniocentesis is done between the 15th and 20th weeks of pregnancy, when there is enough amniotic fluid for testing.

To compare these two tests:

  • CVS can be done earlier in pregnancy than amniocentesis, which gives you more time to make decisions and less time to worry. If you would end the pregnancy based on test results, this would be safest and easiest in the first trimester.
  • CVS does not test for neural tube defects. If you have CVS, you can have a blood test in the second trimester to find out if you are at increased risk of neural tube defects. If the blood test suggests a problem, it is followed by an ultrasound of the fetus.
  • Results of CVS are ready within 1 week. It can take from 2 weeks to 1 month to get the results of amniocentesis.
  • When done by highly trained providers, both tests have about the same risks of miscarriage. In a study of highly trained providers, the risk from amniocentesis and from CVS was about 1 in 400.2 Other studies have shown higher risks, between 2 and 4 in 400.3 This greater risk may be more likely in medical centers with less experienced providers, especially for CVS.
  • CVS is not available in all areas. It requires more training and is harder to do than amniocentesis.

If you need more information on prenatal testing, see the medical tests:

  • Chorionic Villus Sampling.
  • Amniocentesis.
  • Fetal Ultrasound.
  • Alpha-Fetoprotein in Blood.

Your choices are:

  • Have CVS.
  • Do not have CVS. You may decide to have another type of testing, such as amniocentesis, or have no genetic testing.

The decision whether to have CVS takes into account your personal feelings and the medical facts.

Deciding about CVS

Reasons to have CVS

Reasons not to have CVS

  • You will be 35 or older on your due date, and you are concerned about the increased risk of genetic problems with the fetus.
  • Your need to know about a problem with the fetus is greater than your concern about the very small risk of miscarriage.
  • You or your partner has a family history of birth defects that can be found with CVS.
  • You or your partner could pass on an inherited disease or chromosome defect.
  • You want to find out about a problem as early as possible either because you might end the pregnancy or because you want time to prepare yourself for having a baby with a problem.

Are there other reasons you might want to have CVS?

  • You are younger than 35 and have no known risk factors for Down syndrome or other problems.
  • You are more worried about the very slight risk of miscarriage following CVS than you are about the genetic defects the test could find.
  • You prefer to wait and have amniocentesis, which is done later in pregnancy.
  • The problems you are worried about are ones CVS can't detect, such as a neural tube defect.
  • Knowing about a problem with the fetus ahead of time would not change whether or where you had the baby.

Are there other reasons you might not want to have CVS?

These personal stories may help you make your decision.

Use this worksheet to help you make your decision. After completing it, you should have a better idea of how you feel about CVS. Discuss the worksheet with your doctor.

Circle the answer that best applies to you.

I would end my pregnancy if I found out that my baby had a severe birth defect.

Yes No Unsure

I would have the baby even if it turns out that he or she has a problem.

Yes No Unsure

My family has a history of genetic disease.

Yes No NA*

I am younger than 35, so I am not too worried that my age is a risk for my baby having a birth defect.

Yes No NA

I have a child with Down syndrome.

Yes No NA

I had a hard time getting pregnant, so I will continue this pregnancy, no matter what.

Yes No NA

If my baby has a problem, I want to have time to get ready.

Yes No Unsure

*NA = Not applicable

Use the following space to list any other important concerns you have about this decision.






What is your overall impression?

Your answers in the above worksheet are meant to give you a general idea of where you stand on this decision. You may have one overriding reason to have or not have CVS.

Check the box below that represents your overall impression about your decision.

Leaning toward having CVS


Leaning toward NOT having CVS

  • Chorionic Villus Sampling (CVS).
  • Pregnancy.


  1. Jenkins TM, Wapner RJ (2004). Prenatal diagnosis of congenital disorders. In RK Creasy, R Resnik, eds., Maternal-Fetal Medicine, 5th ed., pp. 235–237. Philadelphia: Saunders.

  2. 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.

  3. Seeds JW (2004). Diagnostic mid trimester amniocentesis: How safe? American Journal of Obstetrics and Gynecology, 191: 608–616.

Other Works Consulted

  • American College of Obstetricians and Gynecologists (2007). Screening for fetal chromosomal abnormalities. ACOG Practice Bulletin No. 77. Obstetrics and Gynecology, 109(1): 217–227.

  • Cunningham FG, et al. (2005). Prenatal diagnosis and fetal therapy. In Williams Obstetrics, 22nd ed., pp. 313–339. New York: McGraw-Hill.

Author Sandy Jocoy, RN
Editor Kathleen M. Ariss, MS
Associate Editor Pat Truman, MATC
Primary Medical Reviewer Sarah Marshall, MD - Family Medicine
Specialist Medical Reviewer Kirtly Jones, MD - Obstetrics and Gynecology
Last Updated November 28, 2008

WebMD Medical Reference from Healthwise

Last Updated: November 28, 2008
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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