Chorionic Villous Sampling
Chorionic Villous Sampling (CVS) is a prenatal test done on pregnant women to test for certain types of birth defects, like Down syndrome. The test was first introduced in the United States in 1983 and has since become a routine procedure offered to women receiving prenatal care.
The test takes out a sample of the chorionic villi of the placenta in the uterus. This test is usually performed during the 10th to 12th week of pregnancy.
Similar to an amniocentesis, chorionic villous sampling is usually done on pregnant women over the age of 35, women with a previous pregnancy with birth defects or with a family history of genetic disorders. Chorionic villous sampling carries a slightly higher risk of miscarriage than amniocentesis so you should be well informed about the procedure.
How is CVS Performed?
There are two types of CVS that are currently done on pregnant women: transcervical CVS and transabdominal CVS.
First you will undress and be asked to lay down on an examination table and place your feet in stirrups. Your abdomen and vagina will be disinfected and an ultrasound will be used to locate your placenta. A speculum is used to open your vagina and your cervix will be wiped with antiseptic.
The physician will insert a catheter (a long, thin tube) through your vagina and cervix to reach the villi of your placenta. Some women have described the feeling as a slight cramp or pinch. After taking a small sample the physician will remove the tube and put the sample in a small dish.
For thirty minutes you will lie on your left side while your baby’s heart rate, your pulse, blood pressure and breathing are monitored.
Depending on your anatomy, your doctor may decide to perform a transabdominal CVS. This procedure is recommended for women who have a retroverted uterus. During this procedure, your abdomen is disinfected and, using the ultrasound, the doctor will insert a needle through your abdomen to reach the villi.
After retrieving the sample, the doctor will check the fetus’ heartbeat with the ultrasound. Your pulse, blood pressure and breathing and your baby’s heart rate will be monitored for thirty minutes.
After any of these procedures, it is recommended to relax for a few hours. If you have any cramping, bleeding or spotting, contact your doctor immediately. The test results should be ready within one to two weeks.