What does the procedure entail?

The CVS test involves taking a sample of the chorionic villi cells, which are found in the placenta; the test is done by using an ultrasound scan to guide the needle (in transabdominal tests) or the tube (in transcervical tests) into place. The test can be done in two ways:

• Transabdominal CVS

The transabdominal CVS test is done by inserting a needle through the wall of the abdomen; the needle will be guided to the womb by the ultrasound scan. Before the needle is inserted, the abdomen will be cleaned thoroughly or reduce the risk of infection. Once the needle has reached a suitable point, a sample of the chorionic villi in the placenta tissue will be collected using a syringe.

• Transcervical CVS

The transcervical CVS test is done by inserting a fine tube through the cervix; the vagina and cervix will be cleaned thoroughly before the needle is inserted to reduce the risk of infection. The tube is guided towards the chorionic villi by the ultrasound picture and then a small sample of the tissue is removed by means of gentle suction. Once the sample has been collected, the tube can be removed.

The type of test you have will usually depend on the position of the placenta; one method may be able to access the chorionic villi more easily than the other method. Your doctor will discuss the options with you. Transcervical CVS test is regarded as more complex and it can be more difficult to get the sample; however it may be preferable for some patients due to the location of their placenta.

Is the CVS test painful?

The CVS test should not be painful, but it may feel uncomfortable. The pain is often compared to menstrual cramps and you may feel discomfort for a few hours afterwards. The transcervical CVS test is often compared to a cervical smear test and it may be more painful for women who have not yet had children. Some women who have the transabdominal test experience mild abdominal pain for a short period of time after the test.

How long does the test last?

The CVS test should usually be completed within about 20 minutes; after the test you may wish to take it easy for 24 hours but you will be allowed to return home after an hour or so; during this time you will be monitored to make sure no complications have occurred as a result of the test. It is normal to experience mild pain and spotting for a few hours after the test.