CVS is an acronym for chorionic villus sampling, a prenatal test in which tissue is taken from an expecting mother's placenta and examined to assess a developing baby's risk for certain genetic defects and chromosomal abnormalities. However, although CVS can detect certain conditions, it cannot predict severity, says the Mayo Clinic. Nor can it rule out every possible condition that might affect a developing child.
Chorionic Villus Sampling
Chorionic villus sampling, or CVS, is a diagnostic prenatal test that offers expecting parents the earliest possible glimpse of their child's genetic makeup. The test is performed between 10 and 12 weeks, says the Mayo Clinic. CVS is an invasive procedure. If your placenta is easily accessible through the cervix, your doctor will insert a slender catheter through the cervix and into the placenta, where it gathers a small amount of tissue. Occasionally, a needle is inserted through the abdomen through the uterus, if the placenta cannot be accessed through the cervix or an expecting mother has an infection such as herpes or chlamydia. The tissue then undergoes laboratory analysis.
What CVS Looks For
CVS detects chromosomal abnormalities, such as Down syndrome, says the Mayo Clinic. It also looks for certain genetic disorders, such as Tay-Sachs disease, as well as cystic fibrosis, hemophilia and muscular dystrophy, says the Centers for Disease Control. CVS does have limitations; it does not permit testing for neural tube defects like spina bifida, in which there is incomplete closure of the spine, says the American Congress of Obstetricians and Gynecologists. Neural tube defects can be identified by amniocentesis, another prenatal diagnostic testing procedure that is generally conducted after the 15th week of pregnancy, says the Mayo Clinic.
Paternity
CVS can also serve another purpose: Establishing your baby's paternity. According to the American Pregnancy Association, the chorionic villi--the tissue taken from the placenta--comes from the fertilized egg, so it has the same genetic features. Due to the risks involved with CVS, it is rarely used for the express purpose of determining paternity. You need a doctor's consent if you wish to use CVS to confirm the identity of your baby's father.
Level of Accuracy
Although false-positive results are possible, CVS testing is highly accurate. CVS is 98 to 99 percent accurate when detecting chromosomal abnormalities and genetic disorders. For purposes of establishing paternity, CVS is accurate 99 percent of the time.
Risks
The main risk of CVS is miscarriage. According to the CDC, this rate can be extremely variable, depending on the facility where the test is performed. The average rate of miscarriage associated with CVS is between 0.5 and 1.0 percent, or 1 out of every 200 and 100 pregnancies, respectively.
CVS and You
If you have reason to be concerned about the health of your developing child, CVS offers a psychological advantage over amniocentesis, says the CDC. CVS is performed during the first trimester, before you begin to feel the baby grow and move. Results of CVS give parents the tools to make a decision to terminate a pregnancy earlier, if they so choose. The Mayo Clinic states that CVS is usually suggested when the results have a significant impact on how you and a spouse or partner arrive at important decisions. Talk to your doctor or genetic counselor to help you weigh the risks and benefits of CVS.
