Key Points

  • Chorionic villus sampling is known as CVS.
  • CVS is a procedure in which a tiny sample of tissue is removed from the placenta, or afterbirth, either by passing a fine needle through the mother’s abdomen (transabdominal) or by passing a fine tube or forceps through the cervix (transcervical).
  • CVS is usually offered to women who have an increased chance of having a baby with a disorder. It is not usually offered on a routine basis.
  • CVS is also used to detect whether or not a baby has a chromosomal disorder, such as Down syndrome.
  • The safest time to have CVS is after 10 weeks of pregnancy.
  • Although CVS is usually done before 14 weeks of pregnancy, it can be done later than this.
  • About 2 in every 100 women (or 2%) who have a CVS from 11 to 13 weeks of pregnancy under ultrasound guidance miscarry as a result of the procedure.
  • An alternative procedure, amniocentesis, has a lower risk of miscarriage and is usually offered later in pregnancy. RCOG information about amniocentesis can be found here.
  • If a disorder is diagnosed, then you should be given information and the opportunity to discuss this with a specialist.
  • You will be asked to sign a consent form before having CVS..