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What is chorionic villus sampling (CVS)?

Chorionic villus sampling (or CVS) is an invasive, diagnostic test that tells for sure if your baby has Down syndrome, trisomy 18 or specific other chromosome differences.

This test is available at specialized centres in Ontario and is typically performed between 11 and 13+ weeks of pregnancy.

Using ultrasound, a small piece of tissue is removed from the placenta for testing, usually through the vagina, but sometimes through the abdomen.

The procedure-related miscarriage rate associated with CVS is approximately 1 in 100 (1%).  It is important to note that any pregnant person can have a miscarriage at this time in pregnancy and that, by having CVS, this chance is increased by 1%.

The  results of CVS are typically available within 2-3 weeks and can vary depending on the specific type of testing ordering by your health care provider.  Most times, CVS will show that your baby does not have Down syndrome or trisomy 18 but it is important to know that CVS cannot find every condition. Even after a normal CVS result, there is a chance of having a baby with a different condition such as a hole in the heart or mental disability.  Remember, most babies are born healthy.

For more details, discuss CVS with your health care provider or contact your local genetics clinic.