Chorionic Villus Sampling (SVS) is a test performed at approximately 12 to 13 weeks gestation to determine whether the fetus has certain genetic conditions. It is often used when the mother is age 35 or older, had abnormal prenatal screening test results, has fetal abnormality detected on ultrasound, or if certain inherited conditions are present in the family of either parent.
Chorionic villus is placental tissue. A small sample is removed for analysis via the maternal cervix or maternal abdomen (most common). Ultrasound is used for guidance during the procedure. Most patients report some discomfort and pressure but the procedure only takes a few minutes and any residual discomfort usually resolves in a few hours. Full, preliminary chromosome test results, are usually available in 48 hours.
While CVS is a common form of testing, and considered safe when performed by an experienced physician, it does carry some risks. Potential complications include miscarriage, bleeding, infection and membrane rupture. CVS does not test for alpha fetoprotein (AFP), a marker for neural tube and abdominal wall defects. Patients who undergo CVS must have a maternal blood screening test in the second trimester to test for AFP.
