Chorionic villus sampling is a type of diagnostic prenatal genetic test. This means that it’s used to confirm whether a chromosomal abnormality is present in the fetus.
When is the CVS Test Usually Done?
Between 10-13 weeks.
Who Typically Needs a CVS Test?
1. Pregnant women 35 years and older.
2. Parents-to-be with a family history of chromosomal abnormalities.
3. Pregnant women whose screening prenatal test results (from the first trimester screening test, the second trimester screening test or the NIPS test) fell into the “high risk” category.
What Happens During the CVS Procedure?
A needle is inserted through the abdomen (or a catheter is inserted through the cervix) and a sample of cells from the placenta is extracted. Although this procedure sounds painful, it’s reportedly not that bad. Results are available within 7-10 days.
Fast Facts About the CVS Procedure:
- It’s performed by either a general OB/GYN or a perinatologist (a high-risk pregnancy specialist).
- Women must be on bed rest for 24-48 hours after the procedure, with restricted activity for 7 days.
- If you’re scheduled for a CVS procedure, your doctor will do a vaginal culture to test for Group B Strep at some point during the 2 weeks leading up to the procedure. Group B Strep (GBS) is a bacterium that can colonize the vagina and/or rectum and cause problems for the baby.
What Will the CVS Test Tell Me?
The CVS test will reveal your baby’s karyotype (i.e. their chromosomal make-up). The karyotype will tell your doctor if your baby has extra or missing chromosomes (or pieces of chromosomes).
Is the CVS Test Accurate?
Yes. It identifies 99% of all chromosomal abnormalities. However, it doesn’t tell you if your developing baby has a neural tube defect (unlike the “genetic” amniocentesis, another diagnostic prenatal testing option). Get Wise(r) about the “genetic” amniocentesis here.
CVS Pros:
- CVS is the earliest diagnostic test that can be done. It’s often performed between 10-13 weeks (vs. the amniocentesis, which is done between 15-20 weeks).
CVS Cons:
- There’s a slightly greater risk of miscarriage with the CVS procedure (vs. with the amniocentesis).
- As mentioned above, the CVS test does not assess for neural tube defects.
Insider Info: At one point, studies showed that the CVS procedure caused limb deformities in a small number of fetuses. After further investigation, this was found to occur only in CVS procedures done before 9 weeks of pregnancy, which yours won’t be. I only tell you this in case you like to Google things.
PediaTip: Before going forward with the CVS test, ask your doctor how many CVS procedures they’ve performed during their career and what the complication rate has been.
The Bottom Line
If your doctor recommends that you undergo a prenatal diagnostic test, ask them whether chorionic villus sampling is right for you.
