Chorionic Villus Sampling

Posted October 2, 2022 by Anusha ‐ 3 min read

Chorionic villus sampling, or CVS testing, is a type of genetic test during pregnancy. It can detect if your baby has certain health conditions. CVS test results are very accurate. CVS and amniocentesis, another prenatal test, can help you make important healthcare decisions.

What is Chorionic villus sampling?

  • Chorionic villus sampling (CVS) is a type of prenatal testing.

  • You may choose to undergo this genetic testing during pregnancy to check your unborn baby (fetus) for health conditions like Down syndrome.

  • It also confirms sex.

  • CVS testing takes a small sample of cells from the placenta, the organ that forms during pregnancy to deliver nourishment to your baby.

  • The cells your healthcare provider removes are called chorionic villi.

  • They’re formed from the fertilized egg, so they usually have the same genes as your baby.

What Chorionic villus sampling identify?

  • CVS can help identify certain genetic diseases, including problems with chromosomes.
  • These cell structures hold the baby’s DNA.
  • CVS can detect if there are extra or missing chromosomes or if any have significant changes to their structures.
  • These types of chromosomal changes can lead to birth defects and other problems.

Conditions CVS tests for include:

  • Down syndrome, or trisomy 21.

  • Cystic fibrosis.

  • Sickle cell disease.

  • Tay-Sachs disease.

  • Trisomy 18, or Edward syndrome.

Benefits of Chorionic villus sampling

There are several benefits of CVS testing:

  • Accurate results: You can rely on CVS test results to make important healthcare decisions.

  • Critical information: You may face a higher risk of having a baby with a genetic disorder or other problem. If so, you and your partner may want to know what’s going on with your baby as soon as possible. Having this information can help you make the best healthcare decisions.

  • Earlier knowledge: You do CVS earlier in the pregnancy than amniocentesis. This helps you make choices at the beginning of the pregnancy. For example, the termination procedure is safer the sooner you do it.

Before CVS testing

  • Before the test, you have genetic counseling with either a certified genetic counselor or maternal-fetal medicine specialist.

  • A genetic counselor discusses the risks and benefits of the procedure with you.

  • You also have an ultrasound to confirm the gestational age (how many weeks pregnant you are).

  • You want to do CVS testing at the right gestational age, when you’re between 10 to 13 weeks pregnant.

How does CVS testing work?

Chorionic villus sampling is not painful, though you may feel some discomfort. There are two ways healthcare providers perform the test:

Transcervical (through the vagina)

  • Your provider inserts a speculum into your vagina.

  • This smooth device is shaped like a duck’s bill and is also used for Pap tests.

  • It allows your provider to widen the vaginal walls.

  • Your provider then inserts a thin, plastic tube into your cervix.

  • Guided by ultrasound, the provider moves the tube to the placenta and removes a small sample of villi.

Transabdominal (through the abdomen, or belly)

  • Again guided by ultrasound, your provider inserts a thin needle through your abdomen to the placenta to remove the cells. This process is like amniocentesis.

  • If your provider uses the abdominal method, you may get local anesthesia to reduce any discomfort.

Risks of CVS testing

  • The risk of miscarriage for CVS and amniocentesis are about the same.

  • The miscarriage risk with CVS is about 1 in 300-500.

  • Infection is another risk. And in rare cases, an infant may have limb deformity related to CVS testing.

  • But most cases of limb deformity have happened when CVS was performed before the 10th week of pregnancy.

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