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What is CVS or Chorionic Villus Sampling?

Chorionic villus sampling (CVS) is a very accurate early antenatal test that detects chromosomal abnormalities. With this diagnostic test, you will have complete certainty whether or not your baby has got a particular condition. 
 
What does it screen for?
CVS (chorionic villus sampling) tests a small piece of the developing placenta – this is known as a villus.  The sample contains the identical genetic information as your new baby. Mums to be use it to test for chromosomal disorders including Downs syndrome (or trisomy 21), trisomy 18 and trisomy 13.  CVS can also determine the gender of your baby with 100% accuracy and also detect genetic diseases, such as sickle cell anaemia as Tay-Sachs.
  
Who gets it done?
CVS is available to pregnant women but it is optional rather than routine. An expectant mum may use the test to determine the paternity of her child. But it’s more common for woman over 35 years of age, as they have an increased risk of carrying a baby with a chromosomal disorder, to choose to have a CVS to determine whether her baby has such a disorder. 
 
The test is also undertaken by women who have knowledge of a genetic disease in their family – some mums to be chosen to have the test on their second child particularly if the first has inherited a life threatening chromosomal disorder. The CVS does not detect or diagnose neural tube defects such as spina bifida. Women who have worrying results from a nuchal translucency screening sometimes choose to have a CVS for a more definitive result.  As it is risky to have an amniocentesis early in pregnancy before the second trimester many women may also opt for CVS.
 
What you do with the information that you glean from the test is extremely tough.  We recommend seeing genetic counselling to you make the decision for you and your family about what is right for you.  

How is a CVS done?
The doctor will take an amount of placental tissue during the CVS. There are two ways to carry out a CVS. The first is by insertion a catheter into the vagina and up through the cervix – this is known as a transvaginal CVS. The second is done by inserting a hollow needle into the abdomen – this is known as a transabdominal CVS. The decision about which one to do, is based on the location of the placenta. In both procedures, the doctor will use an ultrasound to guide the catheter or needle to the correct location. 
  
At what stage in pregnancy is a CVS done?
The CVS is carried out between weeks 10 and 12 of pregnancy.  This early timing is the main advance of the CVS because not only is it a conclusive diagnostic test but it is performed earlier than the amniocentesis which isn’t usually performed until between weeks 15 to 20.   The earlier testing allows for earlier intervention if that is something that is wanted.
 
Are there any risks?  
As with amniocentesis, CVS increases your risk of miscarriage. You have a one percent higher risk of having a miscarriage than if you didn’t have the procedure. The more experienced the doctor that carries out the procedure, the lower the risk so it is worth seeking out a doctor who performs the procedure frequently and who can offer lower percentage risk.
 
You will be given an injection of anti-D immunoglobin Rhophylac after the procedure if you are Rhesus negative. This is because there is a risk that your blood could mix with fetal blood during the procedure.
 
Are there any after effects?
A CVS is an emotionally draining experience and you are bound to be exhausted after it.  It also isn’t unusual to experience some cramping afterwards.  Sometimes this is accompanied by vaginal bleeding. Speak to your doctor if you experience either and/or experience any high temperature or fever after the procedure as this could point to an infection. 
 
 
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