CVS (Chorionic Villous Sampling)
After ten weeks of pregnancy, through a procedure known as CVS, a tiny sample of the early placenta can be obtained and chromosomal studies of the fetus can be done. This sample contains chorionic villi, which are the cells that later become the placenta. They have the same DNA as the fetus.
The advantage is earlier detection of a chromosome abnormality. The disadvantage is that 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, those with a previously affected child, if the nuchal translucency results come back positive for an increased risk of a fetal genetic problem or if the Non Invasive Prenatal test comes back positive.