CVS (Chorionic Villous Sampling)

After ten weeks of pregnancy, through a procedure known as CVS, a tiny sample of the placenta can be removed and chromosomal studies of the fetus can be done. The chorionic villi are the cells that later become the placenta.

The advantage is earlier detection of a chromosome abnormality. With CVS there is a slightly higher risk of miscarriage compared to amniocentesis, about 1 percent overall.

Due to this elevated risk, we tend to advise CVS only when the likelihood of a genetic abnormality is increased, such as for pregnant women at or beyond age 38-40, those with a family history of a genetic defect, or those with a previously affected child.