CVS stands for chorionic villus sampling. This is a procedure that can be done where there is a needle introduced either abdominally or vaginally, in order to collect a little piece of placenta. The placenta is made from both baby and mom, so by getting the chorionic villa of the placenta, we can actually ascertain the baby's chromosomal makeup. This is a test to rule out Down Syndrome, Trisomy 18, and any other chromosomal abnormalities. This is done between ten and fourteen weeks, as opposed to an amniocentesis which is a needle introduced abdominally to collect the amniotic fluid of the baby, which also can tell the chromosomal make up of the baby by separating the cells from the baby and the fluid. The amniocentesis, however, has to be done after sixteen weeks. The big advantage of the CVS is that the information can be ascertained at an earlier time, as opposed to an amniocentesis. However, the advantage of the amniocentesis, is that the miscarriage rate is half of that of a CVS.