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Chorionic Villus Sampling (CVS)

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What is CVS?

CVS is a procedure where a small amount of the placental tissue from the developing pregnancy is removed via a needle. It is then sent to the laboratory for testing. Chorionic villi are part of the developing placenta and, as such, are fetal cells. By obtaining some of these cells early in pregnancy, it is possible to assess the chromosomal make up of the fetus. CVS is a very similar procedure to amniocentesis, except that the amniotic sac is not entered. The test is usually done at 11-13 weeks and has been performed world-wide since 1983.

Reasons for the procedure

In New Zealand, women are offered screening with a combination of an ultrasound scan (nuchal translucency) and a blood test to assess the risk of the fetus having Down Syndrome (Trisomy 21). Women who have had a high risk result with this screening may wish to have a CVS to determine whether the fetus has this genetic abnormality. Some women may not have a high risk of genetic abnormality but wish to have and CVS for reassurance.

Before the procedure

No special preparation is required for a CVS. A full bladder is not usually necessary for the scan except when the uterus is tipped well back into the pelvis. Sometimes there is some discomfort after the procedure, so it is a good idea to have your partner or a support person to drive you home.

During the procedure

An ultrasound scan is performed to determine the position of the placenta. Sometimes the procedure cannot be performed, usually when the placenta is not easily accessible. In this case, an amniocentesis will be recommended at 15 weeks.

After scanning, the skin is cleaned with a sterile solution and sterile sheet placed over the abdomen. Local anaesthetic is injected into the skin and muscle of the abdominal wall to numb the tissues. A very fine needle is then inserted through the abdominal wall into the uterus using ultrasound as a guide. A syringe is attached to the needle and, using suction, placental cells are then withdrawn and the needle is removed. The procedure only takes 2-5 minutes. This procedure is mildly uncomfortable, similar to having a blood test.

After the procedure

  • There may be some soreness around the needle site.
  • Please ensure you have someone to drive you home.
  • It is a good idea to have a quiet day after the procedure.
  • If you have any vaginal blood or fluid loss, you should contact your LMC (Lead Maternity Carer) immediately.
  • The results of your CVS will go to your LMC and will take 10-14 days. You can also choose to find out the sex of your baby.

Limitations of the procedure

This test will not diagnose many abnormalities e.g. cleft lip and palate, spina bifida and cystic fibrosis. Careful scanning will be used to screen for structural abnormalities and an anatomy scan at 18-20 weeks is recommended.

To make an appointment

To book an appointment, please call our nurse on (09) 520 9550 ext 7090, or email her at

Further information, including the testing process, will be given at the time of booking.

To download a general information sheet on CVS, click the link on the left of this page.

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