Chorionic Villus Sampling (CVS)

Chorionic villus sampling examines a small placental tissue sample to provide early diagnostic information about selected genetic and chromosomal conditions. Chorionic villus sampling, also called CVS, is a prenatal diagnostic test. A clinician removes a small sample of chorionic villi, which are tiny parts of the placenta, through the cervix or through the abdomen. The cells can be examined for selected chromosome or inherited genetic conditions. CVS is different from a screening test: it is used to seek a diagnosis when testing is appropriate, but it does not assess every possible condition.

Before the procedure, the clinician reviews your pregnancy, explains the reason for testing, and uses ultrasound to check the placenta and pregnancy. During CVS, ultrasound guides a fine needle through the abdomen or a narrow instrument through the cervix to collect placental cells. The sample goes to a laboratory. Results may arrive in stages, because some analyses are quicker than more detailed genetic testing. Your clinician explains what each result can and cannot show.

CVS is an invasive procedure, so your clinician discusses possible bleeding, infection, fluid leakage, or pregnancy loss before you decide. The route used depends on the placenta's position, your pregnancy, and the clinician's assessment. Tell the team about bleeding, fever, severe pain, or fluid loss after the procedure, because these symptoms need prompt clinical advice. The test itself cannot treat a genetic condition.

You can discuss whether diagnostic information would help you prepare, plan care, or make decisions during pregnancy. You may choose CVS, consider another diagnostic test such as amniocentesis, or decide not to have an invasive test. Ask what condition the laboratory will examine, when results are expected, and what support is available while you wait.

CVS samples the placenta rather than the baby's body directly. It is usually offered earlier in pregnancy than amniocentesis, although timing and suitability depend on individual circumstances. A result may be clear, may need further clarification, or may not answer every question. Genetic counselling can help you understand possible findings and their implications.

CVS may be discussed when screening suggests a higher chance of a chromosome condition, when a family history indicates an inherited condition, or when a previous pregnancy or child was affected. A person who carries a known genetic change may also be offered targeted testing. The decision is personal and should reflect your values, the available test, and how you would use the information.

The team confirms the pregnancy and placenta with ultrasound, cleans the area, and collects the sample using the safest suitable route. You may feel pressure or cramping. Afterward, you are observed briefly and given instructions about activity, symptoms, and how results will be communicated.

Mild cramping or light spotting can occur after sampling. Rest if you need to and follow the clinic's instructions. Contact your maternity team promptly for heavy bleeding, worsening pain, fever, contractions, or fluid loss. Results may be delivered by phone, appointment, or another agreed method, with follow-up arranged if the laboratory needs more information.

The main limitations are that CVS cannot detect every condition and that a placental result may occasionally need interpretation or follow-up testing. Procedural risks include bleeding, infection, fluid leakage, and pregnancy loss. Your clinician can explain how these risks relate to your pregnancy and why the test has been offered.

Options can include continuing with non-invasive screening, having amniocentesis later in pregnancy, or declining further testing. The right option depends on the question being asked, the timing, and how much diagnostic certainty you want. [Amniocentesis](/treatments/pregnancy-and-birth-care/amniocentesis/) is another diagnostic procedure, while [Down Syndrome](/conditions/down-syndrome/) explains one condition that prenatal testing may assess.

Look for a maternity or fetal-medicine service that provides prenatal diagnosis and genetic counselling. Bring your screening reports, family history, medication list, and questions about timing and results. A specialist can explain the procedure route, laboratory scope, and follow-up before you consent.