Chorionic villi are small, fern-like projections of the placenta, the organ that supplies oxygen and nutrients to a developing fetus. Because they usually possess the same DNA as the baby, they can be used in genetic testing.
What is Chorionic Villus Sampling (CVS)?
Chorionic villus sampling (CVS) is a diagnostic procedure that is used to detect chromosomal abnormalities and some inherited genetic conditions. It can be performed in the 1st trimester of pregnancy—typically between 12-13 weeks.
What are the Benefits and Risks of CVS?
The CVS prenatal test can provide early diagnosis of genetic conditions, so that you can make healthcare decisions sooner.
Risks of the procedure include:
- Miscarriage: there is a small risk of miscarriage (<1%)
- Infection: rarely, there may be a risk of infection in the uterus
- Injury to the fetus: there is a very small risk of injury to the fetus during the procedure
- Bleeding: vaginal bleeding after the procedure will usually resolve on its own
Why Is Chorionic Villus Sampling Performed?
CVS tests can aid in the diagnosis of genetic conditions that include cystic fibrosis, sickle cell disease, Tay-Sachs disease, and numerous chromosomal conditions such as Down syndrome, Trisomy 13, and Trisomy 18. It is very accurate.
Who Should Consider Chorionic Villus Sampling?
You may be referred to a maternal-fetal medicine specialist for a CVS test if you are at risk of having a baby with a genetic health condition or if there are concerns based on ultrasound findings or family history.
Risk factors include:
- You are 35 years or older
- You or your partner have a family history of genetic conditions
- You already have a child with a genetic condition
The CVS Procedure: What to Expect
Chorionic villus sampling (CVS) involves collecting a small sample of cells from the placenta for testing. The sample, taken from the placenta, contains cells that share the fetus’s genetic material. It can be obtained either transvaginally through the cervix or through the abdominal wall, depending on various factors. After collection, the sample is sent to a laboratory, where the cells are grown in a culture for about seven days.
You should arrive at your appointment for this procedure with a full bladder.
Understanding the Results of Chorionic Villus Sampling
Preliminary results (known as FISH analysis) on the number of chromosomes 13, 18, 21, and sex chromosomes can be available within 72 hours. Additional testing for specific inherited conditions may take several weeks to process.
Your genetic counselor or maternal-fetal medicine physician will follow up with you to discuss test results and any follow-up testing that is recommended.
CVS vs. Amniocentesis: Key Differences
Amniocentesis is a similar type of prenatal test that is typically performed between 16 and 20 weeks of pregnancy. It involves using a thin needle through the woman’s abdomen, guided by ultrasound, to collect a small sample of amniotic fluid. The amniotic fluid contains fetal cells, which are then sent to a laboratory for analysis.
While CVS can be performed earlier in a pregnancy than amniocentesis, it is not able to provide information on neural tube defects as it is a test of the placenta only (unlike amniocentesis, which is a test run on fetal cells and amniotic fluid). A follow-up blood test may be required to screen for those conditions.
Your pregnancy healthcare provider or maternal-fetal medicine specialist can discuss the risks and benefits of each procedure to help you determine which may be best for your situation.
When Is CVS Performed During Pregnancy?
CVS is typically performed between 12-13 weeks of pregnancy. The test is not a standard part of prenatal care and is performed by a specially-trained maternal-fetal medicine (MFM) specialist.
Finding a Specialist for Chorionic Villus Sampling
Your OB-GYN or midwife can provide a referral to one or more MFM specialists in your area. Please be aware that not all MFM physicians perform CVS. You are encouraged to discuss coverage requirements with your insurance company prior to scheduling an appointment.
Book An Appointment!
If you have been referred by your primary care provider, OB-GYN or other healthcare provider, please call our office to schedule an appointment. Our dedicated team will help you understand what information to provide in advance to ensure you see the care best suited to your condition.
Please find the patient information form for CVS here.