Chorionic Villus Sampling (CVS)

What is chorionic villus sampling?
Chorionic villus sampling (CVS) is a procedure in which a small sample of tissue is removed from the placenta early in a pregnancy. The genetic information (chromosomes) in this tissue is the same as the baby's. Genetic specialists analyze the tissue. It can help them predict early in a pregnancy whether the baby has a chromosome disorder, such as Down's syndrome.

CVS is an alternative to amniocentesis. Amniocentesis is a procedure in which fluid is sampled from the sac surrounding the baby. CVS can be done several weeks earlier than amniocentesis. It is used to test for many of the same disorders that amniocentesis tests for. Unlike amniocentesis, however, CVS cannot detect neural tube and spinal defects. This limitation is less important when a mid trimester ultrasound is performed.

Who does this test?
Our office does not offer this test, but we can arrange for the test to be done by one of several experienced specialists.

When is it used?
You may consider having CVS because:
You (the mother) will be 35 years old or older on the due date.

Your family or you have a history of a pregnancy or child with a chromosome problem, such as Down syndrome or birth defects.

Your family has a history of mental retardation or inherited disease such as Tay-Sachs, sickle cell anemia, or cystic fibrosis.

You have male relatives with diseases such as hemophilia and muscular dystrophy.

What happens during the procedure?
CVS is performed either through the cervix (transcervical CVS) or through the abdomen (transabdominal CVS).

In the transcervical procedure, a thin plastic tube is inserted into the vagina and through the cervix to reach the placenta. Ultrasound is used to help guide the tube. A small sample of placental tissue is withdrawn.

In transabdominal CVS, a needle is inserted through the abdomen and uterus and into the placenta. Ultrasound is used to help guide the needle. A small amount of tissue is withdrawn into a syringe. The procedure is similar to amniocentesis.

What are the benefits of this procedure?
The main advantage of CVS is that it is performed earlier in pregnancy than amniocentesis. Amniocentesis is usually done during the 15th to 18th weeks of pregnancy. With CVS, you can have the results of genetic tests before the 14th week.

What are the risks associated with this procedure?
The biggest risk is miscarriage after the procedure. Miscarriages occur after CVS in about 1 of every 100 procedures. This is slightly higher than the risk with amniocentesis, which is about 1 in 200 procedures.

Other complications that can occur from CVS are bleeding, cramping, leaking of amniotic fluid, and infection. The risk of these is rare, about 1% or less. There may be an association between CVS and limb reduction and problems with the baby's jaw. Ask your health care provider about this.

Rarely, it is not possible to obtain an accurate result from CVS. In these situations, amniocentesis is usually recommended