Screening
Chorionic Villus Sampling
Chorionic villus sampling (CVS) is a diagnostic pregnancy test that takes a small sample of the placenta to check for chromosomal and genetic conditions, earlier than amniocentesis.
Quick answer
Chorionic Villus Sampling: what it is and what the results mean
CVS involves taking a small sample of chorionic villi — tissue from the developing placenta — using a needle through the abdomen or a fine tube through the cervix, guided by ultrasound. The tissue contains the baby’s genetic material.
- Why it is done: It is offered as a diagnostic test, usually after a higher-chance screening result or where there is a known family risk, to confirm or rule out conditions such as Down’s syndrome and certain inherited disorders.
- Understanding results: Because it tests the baby’s genetic material, CVS gives a diagnostic answer for the conditions checked, earlier in pregnancy than amniocentesis, supporting informed decisions.
What it is
CVS involves taking a small sample of chorionic villi — tissue from the developing placenta — using a needle through the abdomen or a fine tube through the cervix, guided by ultrasound. The tissue contains the baby’s genetic material.
Why it is done
It is offered as a diagnostic test, usually after a higher-chance screening result or where there is a known family risk, to confirm or rule out conditions such as Down’s syndrome and certain inherited disorders. It can be done earlier than amniocentesis.
What to expect
It is usually done from about 11 weeks. Under ultrasound guidance, a sample is taken through the tummy or the cervix; it may cause brief cramping. Initial results can come within a few days, with full results later.
Understanding the results
Because it tests the baby’s genetic material, CVS gives a diagnostic answer for the conditions checked, earlier in pregnancy than amniocentesis, supporting informed decisions.
Good to know
Risks and limitations
It carries a small risk of miscarriage, similar to amniocentesis, along with rare risks of infection. Occasionally the result is unclear and a follow-up test is needed. It is offered as a choice after careful counselling.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Chorionic Villus Sampling: frequently asked questions
How is CVS different from amniocentesis?
CVS samples the placenta and can be done earlier (from about 11 weeks), while amniocentesis samples the fluid around the baby from about 15 weeks. Both give diagnostic answers with a small procedure risk.
Why choose CVS over waiting for amniocentesis?
CVS can be done earlier in pregnancy, giving results sooner, which some people prefer. Your specialist will discuss the timing, risks and which test suits your situation.
Related tests
Other screening investigations
Sources
Where this is drawn from
- NHS — Screening and pregnancy
- NICE — antenatal and screening guidance
- UK National Screening Committee
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