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 1 minute and afterwards we check that the fetal heart beat is normal.
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 seek medical advice.
When can I expect to get the results?
- The results for Down's syndrome and other major chromosomal defects are usually available within 3 days. The results for rare defects take 2 weeks. As soon as we get the results, we will call you to let you know.
Will the procedure need to be repeated?
- In approximately 1% 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 1% 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 the next 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 we never perform CVS before 11 weeks.