Chorionic villus sampling - CVS, Reasons, Procedure and Preparation for Chorionic villus sampling

CVS or Chorionic villus sampling

Chorionic villus sampling (CVS) is a prenatal test conducted in the early stages of pregnancy in order to determine if the fetus has any chromosomal abnormalities. The test derives its name from chorionic villi, which are small, finger-like growths of cells in the placenta that share the same genetic material as the developing fetus. A sample of these villi are extracted from the uterus and tested to check if there are any genetic defects in the fetus. Chorionic Villus Sampling test is usually conducted between the 10th and the 12th week of the first trimester.

Reasons for Chorionic villus sampling

Chorionic Villus Sampling test is highly advisable in those cases where either parent has a family history of genetic disorders such as hemophilia, sickle cell disease, and thalassemia, Down syndrome or Tay - Sachs disease. The risk of such disorders is also significantly higher if the expectant mother is over the age of 35 years. Your doctor may also suggest that you get this test done in case there are any abnormalities in the ultrasound report. The test is generally conducted before amniocentesis is done (between the 15th and the 20th week of pregnancy) in order to detect genetic anomalies early in the pregnancy and give the parent(s) ample time to decide if they want to go ahead with the pregnancy.

Preparation for Chorionic villus sampling

There is no special preparation that you have to take for the test. Consult your doctor after the reports of your ultrasound tests come in and make an appointment with her well in advance so that you can get the CVS test done before the 12th week of the pregnancy. Also, seek the advice of your doctor regarding the risks and limitations of this test beforehand. You may be asked to go in for genetic counseling along with your partner. On the day of the test, you would be required to drink adequate water or other fluids and refrain from urinating just before the procedure in order to get a clear ultrasound image of the reproductive tract.

Procedure to Conduct Chorionic villus sampling

The actual procedure involves the collection of a small sample of placental tissue from the chorionic villi. This is done by introducing a catheter either through the cervix or the abdomen depending on the position of the uterus as it is imaged through the ultrasound test. The ultrasound image guides the pathologist to guide the thin needle through the safest path and collect CVS test sample without damage to the placenta or the amniotic sac.