Chorionic Villus Sampling (CVS): Benefits and Risks

Chorionic Villus Sampling Benefits and Risks

March 1, 2019

Chorionic Villus Sampling Benefits and Risks

Chorionic Villus Sampling Benefits and Risks
Chorionic Villus Sampling Benefits and Risks

If you’re pregnant and considering genetic testing, or it’s been recommended to you by your doctor, you may have already heard of amniocentesis, one of the most common prenatal tests that’s usually performed during your second trimester. But you may not be as familiar with chorionic villus sampling, another prenatal test that can be done a bit earlier, available during your first trimester.

We’re laying out the facts on why you might consider a CVS, what to expect during the procedure and the benefits and risks of this diagnostic test.

What is Chorionic Villus Sampling?

Chorionic villus sampling, also called CVS, is a prenatal diagnostic test where a small sample of tissue from the placenta is analyzed to provide information about a baby’s genetic makeup. A CVS tests for chromosomal abnormalities and certain birth defects and genetic conditions, including conditions such as Down syndrome, Tay-Sachs and cystic fibrosis.

The test gets its name from the chorionic villi, the part of the placenta where the sample tissue is extracted. Chorionic villi are small pieces of placental tissue and contain the identical genetic makeup as the fetus.

Why is a Chorionic Villus Sampling Done?

CVS is most often done for two reasons: if test results may impact the management of your pregnancy, or if the results would affect your decision whether or not to continue a pregnancy. You may choose to undergo a CVS if:

  • You’re 35 or older.
  • You had abnormal results from a first-trimester prenatal screening test or an ultrasound.
  • You have a family history of a genetic condition or your partner is a known carrier.
  • You had a chromosomal condition in a prior pregnancy.

When is a Chorionic Villus Sampling Done?

Unlike an amniocentesis, another prenatal diagnostic test, CVS is done early in pregnancy. Chorionic villus sampling can be performed as early as 10 weeks and up until about 13 weeks of pregnancy.

What to Expect During the Procedure

Chorionic villus sampling involves using a needle, guided by ultrasound, to collect a sample of the placental tissue. You’ll be awake for the procedure and will have to lie still on an exam table. Prep time for a CVS test may be about 10-15 minutes, but the procedure itself generally takes only a minute or two.

There are two methods your doctor can use to perform a CVS test:

  • Transabdominal CVS. A transabdominal CVS test is performed via your abdomen. Your doctor will clean the area with an antiseptic and use an ultrasound to guide a long, thin needle through your abdominal wall and into your uterus. (It’s common to feel some stinging and cramping when this occurs.) The tissue sample will be extracted, and the needle will be removed.
  • Transvaginal CVS. A transvaginal CVS test is performed via the vagina. Your doctor will clean your vagina and cervix with an antiseptic, and will then use a speculum to open your vagina. From there, a catheter (a thin, hollow tube) will be inserted through your cervix while your doctor monitors the position of your fetus via ultrasound. When the catheter reaches the placenta, your doctor will use gentle suction to remove a small tissue sample.

Which method is used depends on the location of the placenta and the position of your uterus. Your healthcare provider will make the call on which is right for you.

Some women report cramping or a small amount of vaginal spotting or bleeding immediately after chorionic villus sampling. You should contact your healthcare provider if these symptoms remain or get worse, or if you experience chills, fever or leaking amniotic fluid after the procedure. And although it’s not medically necessary, some women decide to relax for the rest of the day following the CVS procedure.

Results from a CVS may be ready anywhere from one to seven days following the test.

Chorionic Villus Sampling vs. Amniocentesis

Chorionic villus sampling and amniocentesis are both diagnostic prenatal tests. There are, however, a few main differences between the two.

Chorionic villus sampling can be performed much earlier in a pregnancy, between 10 weeks pregnant and 13 weeks pregnant, whereas amniocentesis is generally performed between 15 weeks pregnant and 20 weeks pregnant.

The tissue that’s being tested is also different—a CVS tests placental tissue, while an amniocentesis tests amniotic fluid. And, unlike an amniocentesis, a CVS cannot test for neural tube defects, such as spina bifida. Results from a CVS are also usually available sooner than those from an amnio.

Chorionic Villus Sampling Benefits

Making a decision around prenatal testing is a very personal one. If you do decide to pursue chorionic villus sampling, there are a few benefits:

  • Accuracy. Unlike prenatal screenings, which tell you if your baby is more likely than others to have certain conditions, a CVS is diagnostic. This means that other than in very rare instances, the results are always correct.
  • Timing. CVS can be done during the first trimester of pregnancy. This gives you more time to research and make decisions around your pregnancy should any abnormal findings be present.
  • Pregnancy management. A CVS can reveal a number of genetic conditions that may impact either the management of your pregnancy or a decision around whether or not to continue it. For some women, this information can be very empowering in what can be an otherwise difficult time.

Chorionic Villus Sampling Risks and Side Effects

The biggest risk associated with CVS is miscarriage; however, it’s important to interpret this risk through a statistical lens if you’re looking for reassurance around the safety of this prenatal test.

According to experts, the risk of miscarriage after chorionic villus sampling is estimated at about 0.22 percent. Another study of nearly 150,000 women found that CVS was not associated at all with a risk of miscarriage. If you’re deciding whether or not to have a CVS and are concerned about miscarriage, speak to your healthcare provider about their specific miscarriage rates, as risks from this procedure can be further mitigated by your doctor’s experience and skill level.

Other risks associated with CVS include infection and Rh sensitization, when some of your baby’s blood enters your bloodstream. (Rh sensitization is preventable by receiving an injection prior to the procedure if you are Rh negative.) There’s also a very small—around 1 percent—chance of a false positive with CVS. If your provider feels this may be the case, they may recommend following up with an amniocentesis in the second trimester to obtain more accurate results.

Chorionic villus sampling can be a reliable and safe prenatal test to provide you with health information about your developing fetus. Don’t hesitate to speak with your doctor or a genetic counselor for more information.

Once you get a CVS test, try to do something enjoy, like get a prenatal massage or have lunch with a friend, to help you relax until you get your results.

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