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Chorionic villus sampling

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Chorionic villus sampling

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Chorionic villus sampling

Definition:

Chorionic villus sampling (CVS) is a procedure for taking a small piece of placental tissue (chorionic villi) from the uterus in the early stages of pregnancy to check for the presence of genetic defects in the fetus.

How the test is performed:

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Depending on where the placenta is located, CVS can be performed through the cervix (transcervical) or through the abdomen (transabdominal). The techniques are thought to be equally safe and effective for obtaining samples. Both the transcervical and the transabdominal CVS are performed with ultrasound guidance.

An abdominal ultrasound is performed to determine the position of the uterus, the size of the gestational sac, and the position of the placenta within the uterus. Your vulva, vagina, and cervix are then cleansed with an antiseptic such as Betadine. For the transabdominal procedure, the abdomen is also cleansed.

The transcervical procedure is performed by inserting a thin plastic tube through the vagina and cervix to reach the placenta. Ultrasound is used to help guide the tube into the appropriate area and a small sample of chorionic villus tissue is withdrawn.

The transabdominal procedure is performed by inserting a needle through the abdomen and uterus and into the placenta. Ultrasound is used to help guide the needle, and a small amount of tissue is drawn into the syringe.

The sample is placed in a dish and evaluated in a laboratory.

How to prepare for the test:

Your health care provider will explain the procedure, its risks, and alternative procedures such as amniocentesis. Genetic counseling is recommended prior to the procedure. This will allow you to make an unhurried, informed decision regarding options for prenatal diagnosis.