A prenatal diagnostic test that detects chromosomal abnormalities in a fetus. Cells from the villi provide chromosome information as do the cells from the amniotic fluid. A CVS test can be performed between the 9th and 12th weeks of pregnancy, providing earlier diagnosis than amniotic fluid studies. Reasons for Procedure Mother is over age 35.
Pregnancy is considered high-risk.
Either parent has a chromosome abnormality. Mother has previously had a child with chromosome abnormality, such as Down syndrome. Risk None expected. Description of Procedure Ultrasound is used to determine the location of the fetus. In one technique used, an anesthetic is injected into the abdominal skin and then a long hollow needle is inserted into the abdomen to withdraw the villi.