What is Chorionic Villus Sampling?

Chorionic villus sampling (CVS) is a form of prenatal diagnosis to determine chromosomal or genetic disorders in the fetus. It entails sampling of the chorionic villus (placental tissue) and testing it for chromosomal abnormalities, usually with FISH or PCR. CVS usually takes place at 11–13 weeks’ gestation, earlier than amniocentesis. 

Possible reasons for having a CVS can include:

• Abnormal first trimester screen results
• Increased nuchal translucency or other abnormal ultrasound findings
• Family history of a chromosomal abnormality or other genetic disorder
• Parents are known carriers for a genetic disorder
• Advanced maternal age. Screening test are usually carried out first before deciding if CVS should be done.

Risk of miscarriage in CVS is about 0.1-0.2%%. Apart from a risk of miscarriage, there is a risk of infection and amniotic fluid leakage.