Chorionic Villus Sampling (CVS)
Chorionic villus sampling (CVS) is a prenatal test that involves taking a sample of tissue from the placenta to test for chromosomal abnormalities and certain other genetic problems.
The placenta is a structure in the uterus that provides blood and nutrients from the mother to the fetus. The chorionic villi are tiny projections of placental tissue that look like fingers and contain the same genetic material as the fetus. Testing may be available for other genetic defects and disorders depending on the family history and availability of lab testing at the time of the procedure.
CVS is usually done between the 10th and 12th weeks of pregnancy. Unlike amniocentesis (another type of prenatal test), CVS does not provide information on neural tube defects, such as spina bifida. For this reason, women who undergo CVS also need a follow-up blood test between 16 to 18 weeks of their pregnancy to screen for neural tube defects.
There are two types of CVS procedures:
- Transcervical. In this procedure, a catheter is inserted through the cervix into the placenta to obtain the tissue sample
- Transabdominal. In this procedure, a needle is inserted through the abdomen and uterus into the placenta to obtain the tissue sample
Another related procedure that may be used to diagnose genetic and chromosomal defects is amniocentesis.
Reasons for a Chorionic Villus Sampling
Chorionic villus sampling may be used for genetic and chromosome testing in the first trimester of pregnancy.
Here are some reasons that a woman might elect to undergo CVS:
- Previously affected child or a family history of a genetic disease, chromosomal abnormalities, or metabolic disorder
- Maternal age over 35 years by the pregnancy due date
- Risk of a sex-linked genetic disease
- Previous ultrasound with questionable or abnormal findings
- Abnormal cell-free DNA test
There may be other reasons for your doctor to recommend a chorionic villus sampling.
Risks of a Chorionic Villus Sampling
As with any invasive procedure, complications may occur. Some possible complications may include, but are not limited to, the following:
- Cramping, bleeding, or leaking of amniotic fluid (water breaking)
- Preterm labor
- Limb defects in infants, especially in CVS procedures done before 9 weeks (rare)
- People who are allergic to or sensitive to medications or latex should notify their doctor.
- Women with twins or other multiples will need sampling from each placenta in order to study each baby.
There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.
If you have questions or concerns with the CVS procedure, call (314) 996-5433 or email us to speak with a doctor.
Certain factors or conditions may interfere with CVS. These factors include, but are not limited to, the following:
- Pregnancy earlier than seven weeks or later than 13 weeks
- Position of the baby, placenta, amount of amniotic fluid, or mother's anatomy
- Vaginal or cervical infection
- Samples that are inadequate for testing, or that may contain maternal tissue
Before the Chorionic Villus Sampling Procedure
Prior to the procedure, your doctor will explain the procedure to you and offer you the opportunity to ask any questions you may have about the procedure. You will be asked to sign a consent form that gives your permission to do the procedure. Read carefully and ask any questions if something is not clear. Generally, there is no special restriction on diet or activity prior to chorionic villus sampling.
You should notify your doctor if:
- You are sensitive to or are allergic to any medications, latex, tape, and anesthetic agents (local and general).
- You are taking medications, both prescription and over-the-counter, as well as any herbal supplements.
- You have a history of bleeding disorders or if you are taking any anticoagulant (blood-thinning) medications, aspirin, or other medications that affect blood clotting, tell your doctor. It may be necessary for you to stop these medications prior to the procedure.
- You are Rh negative. During the CVS procedure, blood cells from the mother and fetus can mix. This may lead to Rh sensitization and breaking down of fetal red blood cells. In most cases, prenatal blood tests will have determined whether you are Rh negative. You may be asked to provide these lab results before the procedure.
You may or may not be asked to empty your bladder right before the procedure. In early pregnancy, a full bladder helps move the uterus into a better position for the procedure. In later pregnancy, your bladder should be empty to minimize the risk of puncture with the amniocentesis needle.
Based upon your medical condition, your doctor may request other specific preparation.
If you need to notify your doctor of any of these items prior to the procedure, call (314) 996-5433 or email us to speak with a doctor.
During the Chorionic Villus Sampling Procedure
A CVS procedure may be done on an outpatient basis, or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor’s practices.
Generally, a CVS procedure follows this process:
1. You will be asked to undress completely, or from the waist down, and put on a hospital gown.
2. You will be asked to lie down on an exam table and place your hands behind your head.
3. Your vital signs (blood pressure, heart rate, and breathing rate) will be checked.
4. An ultrasound will be performed to check the fetal heart rate, and the position of the placenta, fetus, and umbilical cord.
5. Based on the location of the placenta, the CVS procedure will be performed through your cervix (transcervical) or through your abdominal wall (transabdominal).
For a transcervical CVS procedure, your doctor will perform the following steps:
1. The doctor will insert an instrument called a speculum into your vagina so that he or she can see your cervix.
2. Your vagina and cervix will be cleansed with an antiseptic solution.
3. Using ultrasound guidance, a thin tube will be guided through the cervix to the chorionic villi.
4. Cells will be gently suctioned through the tube into a syringe. You may feel a twinge or slight cramping. More than one sample may be needed to obtain enough tissue for testing.
5. The tube will then be removed.
For a transabdominal CVS procedure, your doctor will perform the following steps:
1. For an abdominal CVS, your abdomen will be cleansed with an antiseptic. You will be instructed not to touch the sterile area on your abdomen during the procedure.
2. The doctor may inject a local anesthetic to numb the skin. If a local anesthetic is used, you will feel a needle stick when the anesthetic is injected. This may cause a brief stinging sensation.
3. Ultrasound will be used to help guide a long, thin, hollow needle through your abdomen and into the uterus and placenta. This may be slightly painful, and you may feel a cramp as the needle enters the uterus.
4. Cells will be gently suctioned into a syringe. More than one sample may be needed to obtain enough tissue for testing.
5. The needle will then be removed. An adhesive bandage will be placed over the abdominal needle insertion site.
If you have questions regarding the types of prenatal tests and procedures and would like to discuss with a doctor, call (314) 996-5433 or email us.
After the Chorionic Villus Sampling Procedure
You and your fetus will be monitored for a time after the procedure. Your vital signs and the fetal heart rate will be checked periodically for an hour or longer.
The CVS tissue will be sent to a specialty genetics lab for analysis. Counseling with a genetics specialist may be recommended depending on the test results.
The following are recommended post-procedure to ensure recovery:
- You should rest at home and avoid strenuous activities for at least 24 hours, or as directed by your doctor.
- You may experience some slight cramping and light spotting for a few hours after CVS.
- You should rest at home and avoid strenuous activities for at least 24 hours. You should not douche or have sexual intercourse for 2 weeks, or until directed by your doctor.
Notify your doctor to report any of the following:
- Any bleeding or leaking of amniotic fluid from the needle puncture site or the vagina
- Fever and/or chills
- Severe abdominal pain and/or cramping
- If a transabdominal procedure was performed, check the bandaged needle site on your abdomen for any bleeding or drainage of fluid.
Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.
If you are experiencing any of the above symptoms after your chronic villus sampling procedure or have questions or concerns, call (314) 996-5433 or email us to speak with a doctor.