Our Outpatient Services

Chorionic Villus Sampling (CVS)

What is chorionic villus sampling?

Chorionic villus sampling (CVS) is a diagnostic biopsy of the early developing placenta performed in the first trimester.  Since the placenta is made up of fetal tissue, a CVS tells you with nearly 100 percent accuracy the chromosomal or genetic makeup of the developing fetus.

What is the difference between a screening and diagnostic test

Unlike the California Prenatal Screening Program which provides a result that identifies the odds a pregnancy will be affected with an abnormality, a diagnostic test such as an CVS will  provide an answer – with nearly 100 percent accuracy – whether the pregnancy is affected with a chromosome disorder or not.

What tests can be performed with the specimen from a CVS?

Most commonly, CVS is used to test for chromosome abnormalities such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18),  trisomy 13, sex chromosome abnormalities and in some  cases, specific genetic disorders such as cystic fibrosis, fragile X or sickle cell disease.

How is a CVS performed?

There are two possible ways to perform a CVS: transabdominal and transcervical.  While some placental locations are accesssible by both methods, usually one method is preferable due to the location of the early placenta.

In the transabdominal approach, a needle is passed through the skin (using local anesthesia) into the early developing placenta under ultrasound guidance. In the transcervical approach, a speculum is placed in the vagina (the same as when a pap test is performed) and a small flexible catheter is guided through the cervix into the placenta under ultrasound guidance.

Are there any risks?

The risk of miscarriage following a CVS is less than 1 in 350.  This risk is less than the spontaneous pregnancy loss rate at the gestational age of the CVS for those people not undergoing a diagnostic procedure.

Are the results accurate?

Approximately 1 percent of the time a rare phenomena known as confined placental mosaicism may be seen.  Should this happen, the results of the CVS are inconclusive and a follow up procedure such as an amniocentesis may be indicated.

What is the advantage of a CVS?

CVS is typically performed between 10-14 weeks.  This provides information about the health of a pregnancy earlier than an amniocentesis (which is usually performed between 15-20 weeks).

Who should consider a CVS?

Women who are:  35 years or older, have a prior pregnancy affected with a chromosome disorder,  have a family history or are at risk for a specific genetic disorder or have received abnormal results from an early screening test (the first component of the prenatal screening program).

 

 

Who should consider chorionic villus sampling?

You should consider chorionic villus sampling if:

  • You are 35 years of old or older
  • You have had a chromosome abnormality in a previous pregnancy
  • You have a family history or are at risk for a specific genetic disorder
  • You have received abnormal results from a screening test