Chorionic Villus Sampling (CVS) is an optional prenatal diagnostic test used to determine if a baby has any chromosomal abnormalities. A thin needle or a flexible tube is used to remove a small piece of placenta tissue (chorionic villi) from the uterus. This procedure may be done vaginally or abdominally, depending on the location of the placenta. The chorionic villi are sent to a laboratory for genetic testing.
Who might consider CVS?
There are a variety of reasons why a pregnant woman might have a CVS. Some reasons include:
Abnormal first trimester screen
Family or personal history of chromosome abnormality or genetic conditions
Previous pregnancy/child with a genetic condition or birth defect
A woman over the age of 35
Any pregnant woman with a desire for a definite chromosome assessment
When is CVS performed?
CVS is typically performed between 11 4/7 and 13 6/7 weeks gestation.
What are the benefits of CVS?
It can detect nearly all chromosomal abnormalities, including Down Syndrome, trisomy 13, trisomy 18 and sex chromosome abnormalities.
The test result provides a yes/no answer for the question: “Does my baby have a chromosome abnormality?”
If indicated, it can detect several hundred genetic disorders, such as Cystic Fibrosis, Sickle Cell disease, and Tay-Sachs disease.
It is performed sooner than an Amniocentesis.
The detection rate for chromosomal abnormalities is over 99%.
What happens during an CVS?
The patient meets with a genetic counselor before the procedure to discuss the risks and benefits of a CVS and to sign a consent form. Ultimately, the patient decides whether or not she would like to have the procedure.
There are two ways a CVS can be completed. The doctor first uses ultrasound to determine the location of the placenta. Depending on the location of the placenta, the doctor then determines the safest method and completes the CVS either through the vagina (transvaginal) or through the abdomen (transabdominal).
Transvaginal: If the placenta is located on the back wall of the uterus, a thin, flexible tube is inserted into the vagina and through the cervix to reach the placenta. With ultrasound guidance, a small sample of the placenta (chorionic villi) is removed.
Transabdominal: If the placenta is located on the front of the uterus, a thin needle is inserted though the patient’s abdomen until it reaches the placenta. With ultrasound guidance, a small sample of the placenta (chorionic villi) is removed.
The placental tissue or chorionic villi typically have the same genetic make-up as the baby. The chorionic villi are sent to the laboratory for genetic testing.
Both methods of performing chorionic villus sampling may take anywhere from 45-60 minutes, although the extraction itself will only last a few minutes. The patient should let her doctor know if she has an active sexually transmitted disease or if she has had any bleeding during her pregnancy.
What does CVS feel like?
Overall, most women do not describe the procedure as being painful. If the procedure is done transvaginally, most women describe it as being similar to a Pap smear. If the procedure is done transabdominally, most women describe a sensation like a needle poke with discomfort similar to menstrual cramps. Some women may experience some mild cramping or light spotting for a few hours after the procedure.
How long to results take?
Final results are usually ready 10-14 days after the procedure. A genetic counselor calls the patient with results as soon as they are ready. A copy of the results is sent to the patient’s doctor or midwife.
Are there any special preparations for CVS?
No. There are no dietary restrictions for CVS. You do not need a full bladder. This test does not require an overnight stay in the hospital.
Patients should avoid heavy lifting (more than 20 lbs), strenuous activity, intercourse or anything inserted vaginally for 2-3 days after having the procedure. If they have the procedure transvaginally, women should avoid swimming or taking a bath for 2-3 days (showers are okay).
After the procedure, the patient needs to call her doctor or midwife if she experiences:
Loss of amniotic fluid vaginally
There is a very small risk of having a complication or miscarriage after the procedure.
Does insurance cover CVS?
It is recommended that you check with your insurance company to verify coverage.
If you additional questions please feel free to contact The Center for Perinatal Care at 608-417-6667.