Who may be offered chorionic villous sampling?
Chorionic villous sampling (CVS) is performed in preference to an amniocentesis if the gestation is less than 15 weeks. Amniocentesis cannot be performed before 15 weeks, because there is insufficient fluid to be able to take an amniotic fluid sample before this time. On rare occasions, a CVS can be performed in preference to an amniocentesis after 15 weeks, particularly if there is not enough amniotic fluid present.
