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Chorionic Villous Sampling (CVS)

What is a CVS?

A Chronic Villous Sampling (CVS) is very similar to an amniocentesis and may be offered if you have a high risk Down Syndrome Screening result or a significant problem in the baby is detected on scan.

The test can be done earlier than an amniocentesis at 12-14 weeks of pregnancy and involves passing a thin needle into the placenta through the uterus under ultrasound guidance to remove a small volume of cells from the placenta. As the baby and placenta originate from the same cell, the chromosomes present in the cells of the placenta should be the same as those of the baby. The lab can then analyse to check the baby’s chromosomes.

What should I expect after CVS?

There may be some discomfort where the needle was inserted for the first couple of days after the procedure, for which you can take 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 CVS?

The risk of miscarriage due to CVS is about 0.5% (1:200) and this is the same as the risk from an amniocentesis. If you were to miscarry due to the test, this would happen within the first 2 weeks of the procedure. In approximately 1% of cases the CVS test will need to be repeated because the results are inconclusive.

CVS is offered between 12 and 14 weeks as an amniocentesis is not offered before 15 weeks because some studies have shown that when amniocentesis is performed before 15 weeks there is a small risk of the baby developing club feet.

Consultant £695

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