It's true that both amniocentesis and CVS slightly increase your risk of miscarriage,though there’s no absolute consensus on how much, exactly. (It’s not always possible to tell if a miscarriage occurred because of the procedure, or if it would have happened regardless.) Doctors usually give a miscarriage risk of one percent with CVS and half a percent with amnio, butunder a skilled and experienced provider, CVS appears to pose no greater risk.(In terms of miscarriage risk, there’s no difference between the transcervcialand transabdominal CVS techniques.) There’s also been some concern about limb defects caused by CVS, but these complications only appeared when the procedure was done before week ten. If you have the test in or after week ten, there’s no need to worry about this.
American College of Obstetrics and Gynecologists. Your pregnancy and birth. 4th ed. Washington, DC: ACOG; 2005.