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.