CVS (Chorionic Villus Sampling) is a technique that is offered for prenatal diagnosis of chromosomal abnormalities associated with advanced maternal age or fetuses that have abnormalities, and can also diagnose certain other genetic diseases. CVS cannot be used to assess the risk for neural tube defects. CVS is performed between 10-13 weeks of pregnancy. During the procedure, a small sample of the placenta, called the chorion, is removed under ultrasound guidance. The main advantage of CVS over amniocentesis (amnio- an alternative to CVS) is that prenatal diagnosis is achieved during the first trimester.
Prior to the procedure, we will have the opportunity to meet with a genetic counselor to review family history, discuss the procedure and ask questions. After genetic counseling, an ultrasound will be performed to determine the location of the fetus, confirm gestational age and locate the placenta. If the placenta is posterior (at the bottom portion of the uterus), a catheter is passed through the cervical opening under ultrasound guidance. The tip of the catheter is directed toward the placenta and a small sample is removed. If the placenta is anterior or fundal (at the top of the uterus), a needle will be passed through the maternal abdomen and uterus into the placental substance, also under ultrasound guidance. Samples are forwarded to the cytogenetics laboratory for processing and diagnosis.
Full results of the CVS are typically available 1-2 weeks after the CVS is performed. However, a FISH (flourescence in-situ hybridization) test will screen for gender and Trisomies 13, 18 and 21, and those results are typically available in 24-72 hours.