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.
Local anesthetic 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 an ultrasound scan.
The procedure lasts 1 minute and afterwards, we check that the fetal heartbeat is normal.
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 most cases, the pregnancy continues without 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.
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.
In approximately 1% of cases, the invasive test will need to be repeated because the results are inconclusive.
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.
