Chorionic villus sampling (CVS) refers to a procedure in which small samples of the placenta are obtained for prenatal genetic diagnosis, generally in the first trimester after 10 weeks of gestation. CVS results are available earlier in pregnancy than amniocentesis results, which provides privacy since the pregnancy has not begun to “show” and shortens the duration of anxiously waiting for information about the fetus. If the results lead to a decision to terminate the pregnancy, the termination can be performed at a gestational age when the procedure is more widely available and has lower risks than mid-second trimester termination procedures. However, CVS results have higher diagnostic uncertainty than amniocentesis and the procedure may be less safe than second trimester amniocentesis.
CVS enables prenatal diagnosis of any condition in which diagnostic cytogenetic, biochemical/molecular, or DNA analysis is possible. The most common reasons for prenatal genetic diagnosis include :
●Maternal age 35 years or older at estimated date of delivery
●Previous child with a chromosome abnormality
●Parent is a carrier of a balanced translocation or other structural chromosome disorder