Risks of a chorionic villus sample
Chorionic villus sampling is one of the invasive methods of prenatal diagnosis, and therefore is associated with some risks. Between 0.5 and 2 percent of all procedures cause a miscarriage, and the test can cause bleeding or premature loss of amniotic fluid.
Chorionic villus sampling results are considered very reliable. It can rarely happen that the removed placental cells do not contain the same genetic material as the child, because a mutation occurred during cell division. In this case, further investigation will be necessary.