CVS & Amniocentesis

Amniocentesis and chorionic villus sampling (CVS) are procedures performed during pregnancy to test your baby’s chromosomes. They are very specialized tests – only certain obstetricians can perform them. Dr Walsh has performed hundreds of CVS and amniocentesis tests.

These tests are recommended if your baby has an increased risk of a chromosomal problem, for example:

Both amniocentesis and CVS are brief out-patient procedures by a Fetal Medicine specialist. The doctor inserts a fine needle into your abdomen under ultrasound guidance. An amniocentesis involves collecting a small amount of amniotic fluid (waters). For a CVS, a small sample of placenta is collected.

CVS & amniocentesis risks

  • Both tests carry a small risk of miscarriage – approximately 1-in-200. Dr Walsh’s own procedure-related risk of miscarriage after these tests is comparable with the best centres internationally.
  • Women whose blood group is Rh-D negative should receive anti-D after the test to prevent blood group antibodies forming.

What is the difference between a CVS and an amniocentesis?

  • CVS can be performed earlier (after 11 weeks) whereas women must be at least 15 weeks for an amniocentesis
  • The two tests provide very similar information and results. However, for certain conditions an amniocentesis is more reliable.
  • Some older studies suggest that the miscarriage risk is slightly higher after CVS, although this probably reflects the fact that CVS is performed earlier in pregnancy.

My pregnancy is low risk but we want testing anyway – is this possible?

  • If a couple feel strongly that they wish to undergo testing then we will support this.

Does a negative amniocentesis or CVS guarantee my baby is healthy?

  • Amniocentesis and CVS cannot test for every condition, genetic or otherwise. While a normal result excludes a large number of chromosome problems, this is not the same as saying that your baby is perfectly healthy.

We offer the full range of specialist obstetric ultrasound scans. Please click on the links below for more information :