Chorion Villus Sampling and Amniocentesis
At Melbourne Ultrasound for Women we offer Chorion villius sampling and Amniocentesis, these tests are used to diagnose or rule out genetic abnormalities in the unborn child. Small samples of tissue are taken from the pregnancy and analysed in a laboratory. Both tests provide the same information. Which test is chosen depends on the stage of pregnancy. CVS is done between 10 and 14 weeks. Amniocentesis between 15 and 22 weeks. The samples are taken using a fine needle passed through the skin guided by the ultrasound equipment and takes 30 to 60 seconds to complete, it is usually less uncomfortable than a blood test.
Why have CVS or Amniocentesis?
The most common reason for having one of these tests is to diagnose or rule out Down Syndrome. This is almost always because of a risk of more than 1 in 300 on screening using ultrasound and blood testing at 12 to 13 weeks. CVS is usually the test performed.
Other reasons include abnormalities that are found on ultrasound either at the 12 to 13 week ultrasound which usually lead to a CVS and 20 week ultrasound which usually leading to an amniocentesis. Sometimes these tests are chosen because of an increased risk of inherited disorders such as cystic fibrosis or thalassemia.
Counselling may be offered by your own doctor or alternatively is available at the practice prior to amniocentesis or other procedures. Counselling is to help you understand both the test itself, plus birth defects and inherited conditions in general; it also allows relevant family medical and pregnancy information to be checked to assess your specific risks. You will then be informed of the risks, benefits and limitations of testing to you. You can choose the course of action that is appropriate for you in view of your own specific family needs and goals. We recommend counselling on a day prior to the procedure to enable you to better consider your options, but it is available also at the practice on the day of the procedure.