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Chorionic Villus Sampling (CVS)
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Chorionic Villus Sampling (CVS)

Chorionic villus sampling (CVS) is a prenatal diagnostic test that checks placental cells for chromosome abnormalities and genetic disorders.

What is chorionic villus sampling (CVS)?

Chorionic villus sampling (CVS) is a genetic test done during pregnancy that checks chorionic villus cells in the placenta to see if your baby has certain health conditions. The test looks for abnormalities in your baby's chromosomes, which are the "packages" in your cells that contain your genes. Because these cells contain the same chromosomes as your developing baby, the test can identify if your baby has an extra, missing, or damaged chromosome.

CVS is a diagnostic test, meaning it can almost always tell for sure whether a baby has a chromosome disorder, unlike a screening test, which only indicates an increased risk.

What is it used for?

CVS is used to diagnose genetic conditions, including:

  • Down syndrome (Trisomy 21): An extra chromosome that affects physical and mental development.
  • Cystic fibrosis (CF): An inherited disease causing mucus buildup in the lungs and other organs.
  • Sickle cell disease (SCD): A group of inherited red blood cell disorders.
  • Tay-Sachs disease: A disorder affecting brain development and sensory function.
  • Trisomy 18 (Edward syndrome): A condition causing growth delays and physical/mental abnormalities.

CVS is performed between the 10th and 13th week of pregnancy. It does not diagnose birth defects like neural tube defects, which require different testing.

Why do I need a CVS test?

Your provider may recommend CVS if you are at higher risk for having a baby with a chromosome disorder, including:

  • Being age 35 or older.
  • Having a family history of a genetic disorder.
  • Having another child with a genetic disorder.
  • Receiving abnormal results on a prenatal screening test.

What happens during a CVS test?

The procedure uses an ultrasound to guide the sampling. There are two methods:

  • Transabdominal: A needle is guided through your abdomen into the placenta.
  • Transcervical: A thin catheter is guided through your cervix to the placenta.

You may feel cramping or stinging during the procedure, and you may experience light vaginal spotting afterward. CVS is not recommended if you have a sexually transmitted infection or vaginal bleeding during pregnancy.

Are there any risks to the test?

While generally safe, risks include:

  • Miscarriage (small risk)
  • Infection
  • Bleeding
  • Rh sensitization
  • Limb defects (very rare)

Contact your provider if you experience chills, contractions, fever, or amniotic fluid leaking.

What do the results mean?

Results are usually available within two weeks. Normal results indicate it is unlikely your baby has the disorder tested for, though it does not guarantee the absence of all health problems. Abnormal results may indicate a genetic disorder. If results are unclear, your provider may recommend amniocentesis, which is performed between the 15th and 20th week of pregnancy.

Frequently Asked Questions

CVS is highly effective for diagnosing chromosomal abnormalities like Down syndrome and specific single-gene disorders such as cystic fibrosis or sickle cell disease if the parents are known carriers. However, it cannot detect neural tube defects like spina bifida, which are typically screened for via maternal blood tests (AFP) and ultrasound. It also does not provide a complete picture of all possible genetic variations, so it is targeted based on the specific conditions being tested for.
CVS is generally as accurate as amniocentesis for detecting chromosomal abnormalities, with a diagnostic accuracy rate of over 99 percent. The primary advantage of CVS is timing; it can be performed earlier in pregnancy (10 to 13 weeks) compared to amniocentesis (15 to 20 weeks). This earlier window allows for quicker results, which can be critical for patients who need to make informed decisions about their pregnancy sooner.
Historically, there was a concern about a slightly increased risk of limb reduction defects, such as missing fingers or toes, when CVS was performed before 10 weeks of gestation. Current clinical guidelines recommend performing the procedure between 10 and 13 weeks to minimize this risk. When performed within this recommended window by an experienced specialist, the risk of limb defects is considered negligible and comparable to the baseline risk in the general population.
While mild cramping and spotting are common and usually resolve within a few days, you should contact your provider immediately if you experience heavy vaginal bleeding, severe abdominal pain that does not improve with rest, fever, or chills. These symptoms can indicate infection or significant bleeding, which are rare but serious risks associated with the procedure.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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