Definition

Chorionic villus sampling is a test that is done to look for chromosomal abnormalities in the baby. It is done during the 9th to 13th weeks of pregnancy.

A sample of tissue from the placenta is removed for testing. This is the organ that provides nutrients and oxygen to the baby. It also removes waste from the baby’s blood.

9 Week Old Fetus in Utero Copyright © Nucleus Medical Media, Inc.

Reasons for Test

This test is done to find out if the baby has a chromosomal abnormality, like Down syndrome. It can also look for problems with the genes, such as cystic fibrosis.

This test may be done when:

• Other tests, such as a first trimester ultrasound or blood tests have abnormal results
• A prior pregnancy had a chromosomal abnormality
• The mother is 35 years old or older
• The mother or partner is a carrier of a genetic problem
• There is a family history of a genetic problem

Possible Complications

Problems are rare, but there are some risks with this test. The doctor will go over some problems that could happen, such as:

• Infection
• Miscarriage
• Rh incompatibility—a sensitivity to the baby's blood, which may enter the mother's bloodstream
• The need to repeat the test, such as if not enough cells were taken

Things that may raise the risk of problems are:

• Having an active infection, such as a sexually transmitted infection
• Carrying more than 1 baby
• Bleeding from the vagina during pregnancy
• Having uterine fibroids
• Having a tilted uterus

What to Expect

Call Your Doctor

Call the doctor if you are not getting better or you have:

• Signs of infection, such as fever and chills
• Blood or fluid leaking from the vagina
• Belly contractions
• New or worsening symptoms

If you think you have an emergency, call for medical help right away.