Chorionic villus sampling (CVS) is an optional prenatal diagnostic test that can offer important information about your unborn baby’s health. It gathers this information from a small tissue sample, taken from the placenta—the structure within the uterus that provides blood and nutrients from the mother to the fetus during pregnancy. The purpose of CVS is to identify possible chromosome abnormalities such as Down syndrome and inherited disorders such as cystic fibrosis.
Your doctor may recommend a CVS test for one of the following reasons:
- Family history of genetic disorders in you or your partner
- A previous child with a genetic disease or chromosomal abnormality
- Maternal age over 35 by the pregnancy due date
- Previous ultrasound with questionable or abnormal findings
- Abnormal cell-free DNA test or other abnormal genetic screening test
- Risk of a sex-linked genetic disease
Chorionic villus sampling is usually done near the end of the first trimester between 10 and 13 weeks from your last menstrual period. It is considered a highly accurate method for identifying hundreds of congenital conditions, but there is a remote chance (1 percent) that it will suggest an abnormality when there is none. This is known as a false positive.
It also does not reveal any information about the degree of severity, nor does it give information about neural tube disorders, such as spina bifida. For this reason, additional tests may be recommended later in your pregnancy.
It is important to note that this test is a personal choice each family should make in consultation with their physician after considering all the risks and benefits. Although it is considered safe, CVS is an invasive procedure and there is a 1 percent risk of pregnancy loss. There are also risks to your unborn child, especially if your child is small for his/her gestational age at the time of the procedure. One possible risk is that your child’s limbs may not fully develop, but this is typically a complication only when the test is performed at less than 10 weeks.
There are advantages to having CVS. This procedure gives expectant parents and physicians the ability to plan early care while a child is still in the womb. If needed, maternal-fetal specialists at Riley at IU Health can work with a multidisciplinary team to plan a delivery that gives babies immediate access to specialized care at birth. Ultimately, having the procedure also gives parents time to anticipate the needs they and their child may have.
What to Expect
What to Expect
Before having CVS, your doctor must know if you are Rh negative. Sometimes a baby’s blood cells may mix with a mother’s during the procedure. If you are Rh negative and your baby is Rh positive, your immune system may produce antibodies against your baby’s blood, which can be harmful to your baby. If this is the case, there are medications that should be given to prevent future complications.
Make your physician aware of any history of bleeding disorders or any blood-thinning medicine you take, both of which may affect the procedure.
Typically, a genetic counselor will meet with you prior to planning the procedure to discuss risk factors, family history, risks and benefits to all available options, etc. After your healthcare providers explain the test’s risks and benefits, you can ask questions and make your decision. If you decide to have the test, you will sign a consent form.
Before the procedure begins, we check your vital signs. To prepare for CVS, you will undress from the waist down and be covered by a sheet, or you will remove all clothing and be given a hospital gown to wear.
The ultrasound performed at the start of the test is a painless part of the procedure. It checks the heart rate of the fetus and the location of the fetus, the placenta and the umbilical cord.
You will rest on your back on an examination table. Your abdomen will be cleansed and prepared for an ultrasound with a gel that helps transmit the sound waves.
CVS testing may be performed one of two ways:
- Transcervical CVS. Using ultrasound guidance, a catheter is inserted through the vagina, into the cervix (the opening of the uterus) and then into the placenta to obtain the tissue sample. It feels very much like having a Pap smear, with some minor discomfort, pressure, and cramping.
- Transabdominal CVS. Guided by ultrasound, a needle is inserted through the abdomen and uterus and then into the placenta to draw a tissue sample. This method may cause some pain and cramping as the needle enters the uterus. The abdomen may be bandaged at the point the needle entered.
Regardless of which method is used, the sample is sent to the lab for evaluation. You may experience some mild cramping or spotting for a few hours. Let your doctor know if you have any of the following symptoms:
- Bleeding or leaking of fluid
- A fever or chills
- Severe abdominal pain
Avoid strenuous activities for at least 24 hours, and avoid douching or having sexual intercourse for two weeks unless otherwise directed by your doctor. You may also receive specific instructions for your situation.
Once the lab report returns, your physician will contact you to share the results. If your family is affected by a disorder or abnormality, maternal-fetal specialists and genetic counselors at Riley at IU Health can provide compassionate support and expert healthcare. Our services are customized to meet the unique needs you or your unborn may have during pregnancy, at birth and all through life.
Key Points to Remember
Key Points to Remember
- Chorionic villus sampling (CVS) takes samples from the placenta to identify hundreds of possible chromosome abnormalities or genetic disorders.
- Although it is highly accurate, in rare cases CVS can suggest a problem where there is none.
- This diagnostic prenatal test is usually done between 10 and 13 weeks of pregnancy.
- Expectant parents should weigh the risks and benefits of having CVS, which can affect a pregnancy.
- CVS is an option, but you may choose not to have it.
Support Services & Resources
Support Services & Resources
These valuable resources can help expectant parents become more informed about prenatal diagnostic tests such as chorionic villus sampling.
Riley at IU Health offers a broad range of supportive services to make life better for families who choose us for their children's care.
The AAFP is an organization for family doctors and publishes a website, FamilyDoctor.org, to share health information with the public, including information about prenatal diagnosis.
This U.S. government website publishes information about many types of health conditions, tests and treatments, and includes a description of prenatal testing.
Visit this National Library of Medicine website to get information about genetic conditions and learn about various types of genetic tests.
As one of the National Institutes of Health supported by the U.S. government, the NICHH studies human development from conception to old age. This site offers a complete description of various kinds of tests that may be performed during pregnancy.