Chorionic villus sampling (CVS) is a test performed during early pregnancy that can find certain problems with your baby (fetus). It is generally performed when either you or the father has a disease that runs in the family (genetic disorder). It may also be performed when you are over age 35-being over 35 increases your chance of having a baby with a chromosome defect.
Chorionic villi are tiny finger-shaped growths found in the placenta. The genetic material in chorionic villus cells is the same as that in the baby's cells. During CVS, a sample of the chorionic villus cells is taken for biopsy and checked for problems. This procedure is generally performed late in the first trimester, most often between the 10th and 12th weeks.
The chorionic villus sample can be collected by putting a thin flexible tube (catheter) through the vagina and cervix into the placenta. The sample can also be collected through a long, thin needle put through the belly into the placenta. Ultrasound is used to guide the catheter or needle into the correct spot for collecting the sample.
If you have a family history of certain diseases, CVS can be used to find genetic disorders and chromosomal birth defects. It can also find chromosomal birth defects, such as Down syndrome. CVS cannot find neural tube defects and it cannot be used to see if the baby's lungs are mature.
Chorionic villus sampling is performed earlier in pregnancy between 10 to 12 weeks. Amniocentesis is usually performed between 15 to 20 weeks. Results of CVS can be available sooner than amniocentesis results. This allows you to know the health of your baby and make an earlier decision whether to continue or end the pregnancy.