CVS – Chorionic Villus Sampling

All you need to know about the procedure of CVS, the risks and what information you can learn by getting a CVS.

One of the few prenatal tests with diagnostic information available to parents in the first trimester, CVS may become more popular than amniocentesis. Here are the answers to your most frequently asked questions about CVS.

When is CVS offered ?

It is typically performed around 10-12 weeks by your doctor or a specialist such as a perinatalogist.

What does CVS look for?

CVS is designed to detect genetic problems such as Down syndrome, cystic fibrosis, hemophilia, and muscular dystrophy with about 98% accuracy. CVS cannot test for neural tube defects such as spina bifida.

How is CVS done?

A tiny sample of the baby’s portion of the placenta that contains genetic information is removed either vaginally through the mother’s cervix or with a needle through the mother’s abdomen. Both require the use of ultrasound for accuracy. CVS is, in essence, the same as taking a biopsy of the placenta. Since the chorionic villi of the placenta have the same genetic material as the baby, the sample can indicate information about the baby’s health. This sample is collected and evaluated in a lab.

Are there risks with CVS?

Previous research indicated a 4% risk of miscarriage after a CVS. In about 1% of cases, it can cause the mother’s water to break. There is a small risk for an infection in amniotic fluid with CVS. Depending on the timing of the test, there is a risk of limb abnormalities or defects with fingers and toes which occurs in about 1 out of every 1,000 to 1,300 babies. The severity of the defects was related to the timing of when the CVS was performed; the earlier the test, the more severe the defects.

There is new research that shows that CVS may in fact, have similar risks to amniocentesis. The study, published in the September 2006 Green Journal, found that the rate of miscarriage over a 20-year period, from 1983 to 2003 was 3.12 % with CVS and 0.83 % with amniocentesis. When other factors were controlled for, (such as mother’s age and gestation), no differences were found.

About 15% of women experience spotting for several days after CVS, which typically resolves. About 6% of women may require an amniocentesis to confirm results.

According to the Cochrane Library (a respected source of evidence based information), CVS is safer if it is done through the wall of the womb versus through the vagina and cervix.

Other facts about CVS you might want to know:

  • CVS has been used as a prenatal test since the 1980’s.
  • If you are Rh negative, you will need a RhoGam shot prior to having CVS.
  • CVS is performed more often (about 95% of the time) for advanced maternal age (over 35) than for any other reason.
  • If you have a retroverted or tipped uterus, a transcervical CVS is not possible.
  • Neither method of CVS is recommended if you have had any vaginal bleeding during your pregnancy.
  • Some women choose CVS over amniocentesis since it can be done earlier, however the risk of miscarriage with CVS is higher.

Be sure to look over information on all prenatal testing options.

Are you planning to have a CVS? Share your thoughts about it.