CVS: How Does the Procedure Work?

A CVS procedure can be done in the doctor’s office by a high-risk pregnancy doctor called a perinatologist. CVS is an outpatient procedure, meaning you can usually go home soon afterward. Most women find that it can be uncomfortable and many compare it to having intense menstrual cramps, but generally do not experience considerable pain beyond that.

The point of the procedure is usually to get tissue from the placenta to send to the lab for testing. The lab can look at the cells from that tissue, and inside those cells at the chromosomes. Approximately 98-99% of the time, the baby and the placenta have the same chromosomes. To learn more about chromosomes, visit our Genetics 101 page.

Approximately 1-2% of the time, the placenta’s chromosomes may be different from the baby’s chromosomes; this is called confined placental mosaicism (or CPM). If the test results show extra or missing chromosomes (called aneuploidy) and the lab is able to confirm that the aneuploidy is caused by CPM, then the most likely thing is that cells with aneuploidy are just in the placenta and not in the baby. The only way to tell this for sure before the baby is born would be to do another test called an amniocentesis.

There are two possible ways that the CVS may be done:

  • A catheter can be used to reach the placenta vaginally
  • A small needle can be inserted into the abdomen to reach the placenta

Whether a CVS is done via the abdomen or vaginally is dependent on many factors, including where the placenta is located and the doctor who is performing the procedure. The procedure generally takes less than a couple minutes from start to finish.

Because CVS is an invasive procedure, there is a less than 1 in 200 (0.5%) chance that it may cause complications that could lead to a miscarriage. This also means that over 99.5% of women who undergo CVS testing do not have a procedure-related miscarriage. To help limit the risk for complications, your doctor may give you special instructions to limit strenuous physical activity for the few days following your procedure. Because of this risk for complications, diagnostic tests like CVS are always optional, and never anything that you would have to do.

Depending on the type of testing that is performed, CVS can look for chromosome conditions, such as Down syndrome, or other genetic conditions, but cannot rule out all birth defects or genetic conditions.

Click here to learn more about scheduling a genetic counseling appointment for pregnancy-related questions.

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  • Because the placenta and the baby come from the same cells, they have exactly the same amount of chromosomes most (98-99%) of the time. In approximately 1-2% of all pregnancies, the placenta can actually have a different chromosome makeup from the baby. This is called confined placental mosaicism (CPM). When…

Last updated on Aug 21st, 2019

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