46 Wimpole Street

London W1G 8SD

020 7935 4450

scan@thelondonultrasoundcentre.co.uk

CVS (Chorion Villus Sampling)

12 to 14 Weeks of Pregnancy


Click on a question to take you to the answer.

What is a CVS?

Why would I need a CVS?

What is usually diagnosed from a CVS?

What additional genetic disorders can be diagnosed from a CVS?

What happens during a CVS?

When can I have a CVS?

What if I have missed the window for having a CVS?

What are the risks when having a CVS?

What are the success rates of your consultants performing the CVS?

How is the sample from a CVS analysed?

When will I receive the results of my CVS?

Do I need to make any preparations before a CVS?

Anything else I should know about the CVS?

What is my next scan after the CVS?

How do I book a CVS?

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What is a CVS?
CVS stands for Chorion Villus Sampling and is a medical procedure performed during early pregnancy to take a small sample of tissue from your developing placenta.

The sample is then analysed in a Genetics Laboratory to diagnose any genetic abnormalities of your unborn baby.

Because this tissue (villi) will eventually form your placenta genetic analysis of the sample will give the same result as if the fetus itself were examined.

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Why would I need a CVS?
A CVS is usually offered on the NHS or privately if you have received a high risk screening from your first trimester screening such as the Nuchal Scan.

However you may wish to have a CVS performed for your own peace of mind.

The choice about whether to have a CVS or not is up to you.

More information on Down Syndrome Screening and diagnostic tests can be found on our About Down Syndrome Screening page.

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What is usually diagnosed from a CVS?
Using tissue obtained during a CVS the Genetics Laboratory usually test for Down Syndome, Edward's Syndrome, Patau Syndrome and a chromosomal analysis.

A CVS can also used to obtain samples for Pre-Natal Paternity Testing.

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What additional genetic disorders can be diagnosed from a CVS?
In addition to Down Syndome, Edward's Syndrome, Patau Syndrome and a chromosomal analysis, Cystic Fibrosis can also be included if there is a family history at no extra cost.

Genetic testing can also be performed for other identifiable problems at additional cost. These supplemantary tests can be included if there is a family history or other children have been born with the condition.

A consultation with one of our Fetal Medicine Specialists or a Consultant Geneticist will be necessary before proceeding with any of the following additional tests:

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What happens during a CVS?
Before the CVS procedure you will be counselled by our Fetal Medicince Specialist and have time to ask any questions. You will also need to sign a consent form which will be fully explained to you.

During the CVS the consultant will pass a fine needle through your tummy into the placental tissue on the outside of your pregnancy sac.

Although this may sound frightening to some in reality the procedure is usually very straighforward, and is performed under continuous ultrasound vision to avoid any threat to your baby.

A local anaesthetic is applied before the needle is inserted to ensure that the CVS carries little discomfort.

The doctor will then draw up a tiny sample of your developing placenta (villi) via a syringe into some sterile pink media.

Much of the appointment time is taken up with preparation and counselling. The actual CVS procedure only takes one or two minutes to perform and is usually over before you realise it.

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When can I have a CVS?
The best time for a CVS is around 12 weeks gestation and is not performed after 14 weeks.

We cannot perform a CVS before 11 weeks because the chances of miscarriage are much higher.

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What if I have missed the window for having a CVS?
If you are later than 14 weeks gestation there is no need to worry as there is an alternative test called an Amniocentesis that is available from 16 weeks.

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What are the risks when having a CVS?
There is a 1% risk of miscarriage associated with having a CVS. This means for every 100 CVS procedures performed it is possible 1 patient would experience a miscarriage and 99 would be expected to progress normally.

Because a CVS is performed during early pregnancy when most miscarriages are more likely to occur naturally the risk may be higher than if an Amniocentesis is performed in later pregnancy.

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What are the success rates of your consultants performing the CVS?
Our consultants sucessfully perform hundreds of CVS procedures every year and their audited miscarriage rates are lower than the national average of 1%.

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How is the sample from a CVS analysed?
The tiny sample is sent to a highly specialised forensic Genetics Laboratory for analysis.

The sample and it is analysed using a process known as PCR (Polymerase Chain Reaction) to obtain a preliminary result.

The specimen is then set up for karyotyping in a culture which usually produces an identical result to the intial PCR.

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When will I receive the results of my CVS?
Preliminary results for Down Syndome, Edward's Syndrome and Patau Syndrome are available in 2-3 days with the culture results following in about 2 weeks.

Results from a full analysis of other requested chromosomal anomalies can also take up to 2 weeks.

Most genetic testing produces a definite answer, however in 1 in 100 of cases the results may prove inconclusive so further consultation or testing may be required.

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Do I need to make any preparations before a CVS?
Yes. Before the procedure is performed we need to know your blood group. If your blood type is Rhesus Negative we will need to be give you an injection of Anti-D after the CVS has been performed.

Please bring written confirmation of your blood group to your CVS appointment. If you are unable to provide documented evidence of your blood group you will need to have a blood type test performed at additional cost.

You do not need to fast before a CVS although you should arrive with a full bladder to allow clear initial imaging. 

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Anything else I should know about the CVS?
We are able to provide conclusive Gender Identification as part of the CVS procedure at no additional cost.

If you'd like to know the gender of your baby please tell the consultant during your appointment as gender isn't routinely reported unless requested.

Please note that we will not perform a CVS solely for the purposes of Gender Identification.  

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What is my next scan after the CVS?
The next routine scan you should expect after a CVS is the 20 Week Anomaly Scan.

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How do I book a CVS?
For bookings information and prices please see our Prices page.

The procedure is only performed by qualified Consultants on certain days so please be prepared to be flexible with your booking date.

Because of the preparation required for this procedure we usually ask for a £100 deposit to secure a CVS appointment.

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