Invasive Diagnostics – Chorion Villus Sampling (CVS) and Amniocentesis (Amnio)
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.
How is amniocentesis done?
- Amniocentesis involves passing a thin needle into the uterus in order to remove a small volume of amniotic fluid. The needle is carefully observed using ultrasound scan.
- The fluid is fetal urine and the amount removed by amniocentesis reaccumulates within a few hours.
- The procedure lasts 1 minute and afterwards we check that the fetal heart beat is normal.
What should I expect after amniocentesis?
- For the first couple of days you may experience some abdominal discomfort or period-like pain. You may find it helpful to take simple painkillers like paracetamol.
- If there is a lot of pain, bleeding, loss of fluid from your vagina 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
What are the risks associated with amniocentesis?
- The risk of miscarriage due to amniocentesis is about 1% and this is the same as the risk from chorion villus sampling. If you were to miscarry due to the test, this would happen within the next five days.
- Some studies have shown that when amniocentesis is performed before 16 weeks there is a small risk of the baby developing club feet. To avoid this risk we never perform amniocentesis before 16 weеks.
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