Chorionic Villus Sampling (CVS)

Why this test may be ordered

• To diagnose chromosome problems such as Down syndrome (Trisomy 21), Trisomy 18 (Edward syndrome), or other genetic diseases like cystic fibrosis, sickle cell disease, and Tay-Sachs disease
• If you are age 35 or older and have a higher risk of having a baby with Down syndrome or another genetic disorder
• If you have a family history of a genetic disorder
• If you have had another child with a genetic disorder
• If you had abnormal results on a prenatal screening test

Preparation and collection

On the morning of the test, you may be asked to drink extra fluids and not urinate. This will fill your bladder, which may help move the uterus into a better position for the procedure.

Your provider will use an ultrasound to check your baby's position and guide the procedure. The test usually takes about 30 to 45 minutes. There are two types: transabdominal (a long, thin needle is guided through your abdomen to take a sample) or transcervical (a thin catheter is guided through your cervix to the placenta to take a sample).

CVS is generally considered to be a safe procedure, but it does have some risks. These include: miscarriage (this is a small risk), infection, bleeding, Rh sensitization (a condition in which your body makes antibodies that attack your baby's red blood cells; if diagnosed during pregnancy, it is easily treatable), and limb defects in the baby (this is very rare). Call your provider if you have chills, contractions, a fever, or amniotic fluid leaking after the procedure.

Understanding results

CVS test results are usually available within two weeks. The results can help determine if your baby has certain chromosome or genetic disorders.

• Normal: It is unlikely that your baby has the disorder that was tested. However, it does not guarantee that your baby won't have any health problems. Limitation: A normal result does not rule out all possible health conditions or birth defects, such as neural tube defects. Next step: Discuss any remaining questions with your healthcare provider.
• Not normal (abnormal): Your baby may have a chromosome or genetic disorder, such as Down syndrome or cystic fibrosis. Limitation: CVS is a diagnostic test that can almost always tell for sure whether a developing baby has a chromosome disorder, but it does not diagnose or screen for birth defects such as neural tube defects. Next step: Talk with your provider about your options and the decisions you may need to make. It may also help to speak to a genetic counselor both before and after you get your results.
• Unclear: The test results were not clear enough to determine whether a disorder is present. Limitation: Occasionally, CVS test results are unclear. Next step: Your provider may recommend amniocentesis, another prenatal diagnostic test performed between the 15th and 20th week of pregnancy.

• CVS can only diagnose certain genetic diseases and does not diagnose or screen for birth defects such as neural tube defects.
• A normal result does not guarantee that your baby won't have any health problems.
• CVS is not recommended if you have a sexually transmitted infection (STI) or have had vaginal bleeding during the pregnancy.
• There is a small risk of miscarriage, infection, bleeding, Rh sensitization, and very rare limb defects in the baby.

What to do next

If your CVS test results were not normal, talk with your provider about your options and the decisions you may need to make. It may also help to speak to a genetic counselor both before and after you get your results. If results are unclear, your provider may recommend amniocentesis.

• What do my CVS test results mean for my baby's health?
• What are my options if the results show a chromosome or genetic disorder?
• Should I speak with a genetic counselor to better understand my results?
• What follow-up tests might be needed if results are unclear?
• How will these results affect my pregnancy care plan?

Evidence source

U.S. National Library of Medicine: Chorionic Villus Sampling (CVS)