CVS stands for chorionic villus sampling, which is a tissue test performed to detect and diagnose birth defects in unborn fetuses. If you're pregnant, your doctor might recommend a CVS if you have certain risk factors. Some potentially serious risks are involved with a CVS, so discuss the test carefully with your physician beforehand.
Description
CVS involves taking a tiny amount of tissue from the placenta in your uterus, explains the University of Maryland Medical Center. After an ultrasound is performed, your doctor will either take the CVS via your cervix or abdomen. The tissue sample will include cells from specific areas of the placenta called the chorionic villi, says the University of Pittsburgh Medical Center. The cells of the chorionic villi in the placenta contain the same genes as your baby's cells and can reveal a genetic defect or disorder, notes the University of Michigan Health System. Like an amniocentesis, CVS can detect chromosomal disorders such as Down syndrome and genetic conditions such as Tay-Sachs disease, hemophilia and hundreds of other disorders.
Timeframe
CVS is typically performed sometime during your first trimester, or about three months of pregnancy, says the University of Pittsburgh Medical Center. Usually, CVS is conducted around the 10th to 12th weeks of pregnancy, notes the University of Michigan Health System. This is five to eight weeks earlier than an amniocentesis is typically performed.
Drawbacks
Although CVS can detect nearly all of the same genetic disorders as an amniocentesis, it cannot detect Rh incompatibility or neural-tube defects, says the University of Maryland Medical Center. Also, unlike an amniocentesis, CVS cannot indicate whether your infant's lungs have matured, adds the University of Michigan Health System. If you need testing for these concerns, you should opt for an amniocentesis. For neural-tube defect testing, you can have a blood alpha-fetoprotein, or AFP, test along with the CVS, notes the University of Pittsburgh Medical Center.
Risk Factors
Your doctor might recommend CVS if you have certain risk factors for having a baby with genetic birth defects. These risk factors include having birth defects in your family or other children, being older than 35 years of age, or having certain other genetic testing that yielded abnormal results, says the University of Pittsburgh Medical Center. The tissue sample collected from the CVS can reveal genetic disorders in the fetal enzymes, chromosomes and DNA, explains the University of Maryland Medical Center.
Warnings
Although the risk level for CVS is about the same as an amniocentesis, you should keep in mind that the procedure for the test can lead to potentially serious complications, warns the University of Maryland Medical Center. After the CVS, you could experience bleeding, ruptured membranes or an infection. You have a 1 in 400 chance of having a miscarriage after CVS, and your risk is higher if the testing is performed via the cervix instead of abdominally, warns the University of Michigan Health System. CVS-related miscarriage risks are slightly higher than those from an amniocentesis, because CVS is performed earlier in the pregnancy. Although rare, CVS can result in fetal limb injuries or deformities, particularly when the test is performed prior to 10 weeks gestation, cautions the University of Pittsburgh Medical Center.
