The clinic can also help when the pregnancy is at increased risk due to family history or consanguinity and when concerns regarding the effects of exposure to potential teratogens arise. Evaluations are carried out in conjunction with the perinatologists at the Froedtert & the Medical College Maternal Fetal Care Center.
Chorionic Villus Sampling (CVS)
There is no "test" available that guarantees you will have a healthy baby. Normal CVS and amniocentesis results help to exclude some potential problems, so they are reassuring. Only after your baby's birth will you know just how healthy he or she is.
The transabdominal approach uses a needle. For this procedure you rest on the examination table. The skin is cleaned with an antiseptic solution. Under ultrasound guidance the needle is passed through your abdominal wall and the wall of the uterus to reach the villi. A syringe attached to the needle is used to suction out a small amount of villi as the needle passes through the villi.
The transcervical approach uses a thin flexible plastic catheter (a hollow tube). For this procedure you rest on your back in a gynecological examination position. A gynecological speculum is inserted into the vagina to enable the cervix (the opening to the uterus) to be seen. The vagina is cleaned with an antiseptic solution, and then the catheter is carefully guided through the cervix under ultrasound guidance to the villi. A syringe attached to the catheter is used to suction out a small amount of villi as the catheter is withdrawn.
If an inadequate amount of tissue is obtained with the first attempt then a second attempt may be undertaken. In studies of CVS the risk of miscarriage rose appreciably with 3 or more attempts (1).
For some individuals the position of the uterus and the villi within the uterus does not permit testing. Waiting one to two weeks for growth to occur may allow testing in many cases. A few individuals will have to wait for an amniocentesis to be performed later in the pregnancy.
If you have had bleeding during this pregnancy, have been told that you have an abnormality of the uterus such as a bicornuate uterus, or have active genital herpes your physician will discuss whether CVS is right for you.
There is a small chance that we may find a mixture of normal and abnormal cells in your CVS. In most instances these abnormal cells are confined to the placenta and are not in the fetus. In these situations we perform an amniocentesis to determine whether the abnormal cells are present in the fetus.
CVS cannot detect a spina bifida and other neural tube defects and therefore we recommend that women have maternal serum alpha-fetoprotein (AFP) screening in addition to CVS. This blood test is performed at 15 to 18 weeks of pregnancy.
Although substantially proven not to be true, there was some concern a number of years ago about a small increase in the risk of fetal limb abnormalities associated with CVS (3).
We will call you and your physician or midwife with your results. We will also send them a copy of your results.
If your results are abnormal, we will spend time with you to discuss them and any additional testing that is recommended.
Your physician will explain the CVS procedure and its risks. We will also explain alternatives such as amniocentesis and no invasive testing, and the risks of those choices. You will then be asked to sign the informed consent form. You may decide not to have the procedure up to the time that we perform the procedure.
Your physician will use an ultrasound examination at the time of the procedure to determine which way will be easiest based on your anatomy, and will discuss the plan with you at that time.
An ultrasound will be performed after the procedure to check the fetus' heartbeat.