Chorionic villus sampling (CVS)
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What is chorionic villus sampling?
Chorionic villus sampling (CVS) is a prenatal test that involves taking a sample of tissue from the placenta, a structure in the uterus that provides blood and nutrients from the mother to the fetus, to test for chromosomal abnormalities and certain other genetic problems. The procedure may be used in the presence of one or more of the following conditions:
- Family history or previous child with a genetic disease, or chromosomal 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
There are two types of CVS procedures:
- Transcervical - a catheter is inserted through the cervix into the placenta to obtain the tissue sample
- Transabdominal - a needle is inserted through the abdomen and uterus into the placenta to obtain the tissue sample
CVS is usually performed 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.
What will happen during the procedure?
A CVS procedure may be performed on an outpatient basis, or as part of your stay in a hospital. Procedures may vary depending on your condition and your physician’s practices.
Transcervical CVS procedure:
- The physician will insert an instrument called a speculum into your vagina to spread the walls of the vagina apart.
- Your vagina and cervix will be cleansed with an antiseptic solution.
- Using ultrasound, a thin tube will be guided through the cervix to the chorionic villi.
- 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.
- The tube will then be removed.
Transabdominal CVS procedure:
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.
- The physician 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.
- 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.
- Cells will be gently suctioned into a syringe. More than one sample may be needed to obtain enough tissue for testing.
- The needle will then be removed. An adhesive bandage will be placed over the abdominal needle insertion site.
Are there any risks?
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
- Preterm labor
- Limb defects in infants, especially in CVS procedures done before 9 weeks (rare)
Notify your physician of any sensitivities of allergies, any medications you or taking, and any history of bleeding disorders.
After the procedure
You and your fetus will be monitored for a time after the procedure. The CVS tissue will be sent to a specialty genetics lab for analysis. 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 two weeks, or until directed by your physician. Notify your physician 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 physician may give you additional or alternate instructions after the procedure, depending on your particular situation.
Counseling with a genetics specialist may be recommended depending on the test results.