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What is Chorion Villus Sampling?
Chorion villus sampling (CVS) involves the examination of chorionic villi (placental tissue). Both the baby and placenta (afterbirth) originate from the same cell and so the chromosomes present in the cells of the placenta are the same as those of the baby.
How is CVS done?
Local anaesthetic is given. A fine needle is then passed through the mother's abdomen and a sample of villi is taken. The needle is carefully observed using ultrasound scan. The procedure lasts 2-3 minutes.
When is it done?
At 11 to 13 weeks.
What should I expect after the CVS?
For the first couple of days you may experience some abdominal discomfort, period-like pain or a little bleeding. These are relatively common and in the vast majority of cases the pregnancy continues without any problems. You may find it helpful to take simple painkillers like Paracetamol. If there is a lot of pain or bleeding or if you develop a temperature please contact your GP or the hospital.
When can I expect to get the results?
The results for Down's syndrome and other major chromosomal defects are usually available within 3-4 days, and for rare defects two weeks. You will be contacted as soon as the results become available.
Will the procedure need to be repeated?
In approximately 1 per cent of cases the invasive test will need to be repeated because the results are inconclusive.
What are the risks associated with the test?
The risk of miscarriage due to CVS is about 0.5 per cent and this is the same as the risk from amniocentesis at 16 weeks. If you were to miscarry due to the test, this would happen within five days. Some studies have shown that when CVS is performed before 10 weeks there is a small risk of abnormality in the baby's fingers and/or toes. To avoid this risk CVS is not performed before 11 weeks.
Do I need to take time off?
It is recommended to rest on the day of the procedure and for 48 hours after.
Why is my blood group relevant?
If your blood group is rhesus negative we will need to give you an injection of anti D following the procedure to prevent the development of rhesus disease in future pregnancies.
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