Sanford Clinic Women's Health
What is a Chorionic Villus Sampling (CVS)?
Chorionic Villus Sampling (CVS) is a prenatal procedure in which chorionic tissue is taken from the developing placenta and examined.
Chorionic villi are made up of cells that develop from the same fertilized egg as the baby. This procedure is performed by a highly trained physician called a Perinatologist. CVS is usually performed between 10 and 13 weeks gestation which is before an amniocentesis is performed (after 15 weeks).
Who should consider having a CVS?
A CVS should be offered to all women who will be over the age of 35 at the time of delivery. As a woman's age increases, so does her risk for having a baby with a chromosome abnormality (see below). In addition, individuals who have had a child with a chromosome abnormality, individuals who know they carry a chromosome rearrangement and women at risk for having a child with a genetic disease should also be offered a CVS. Finally, women who have had an abnormal 1st trimester screen or an early abnormal ultrasound, such as an increase Nuchal Translucency, should consider this procedure.
What can be detected through a CVS?
Chromosome Abnormalities
The human body is made of millions of cells. Inside each cell are structures called chromosomes that store the genetic “blueprint” for each of us. The body uses
these instructions for everything from eye and hair color to growth and development. Normally, each human cell contains 23 chromosome pairs for a total of 46 chromosomes. A missing or extra chromosome can cause problems in how a baby grows and develops, and in many cases can lead to birth defects, mental retardation, or both.
Inherited genetic disease
Some families are at increased risk for having a baby with an inherited genetic disease. Examples of genetic diseases include muscular dystrophy, cystic fibrosis, and sickle cell disease. After an amniocentesis is performed, the cells are sent to a laboratory to perform a specific genetic test for the disease in question.
How is a CVS performed?
The patient first receives individualized genetic counseling and a discussion about the risks and benefits of the procedure. At Sanford Clinic Maternal-Fetal Medicine, you will discuss this information with a certified Genetic Counselor or a Perinatologist who will not only provide you information, but also will allow you an opportunity to have your questions addressed.
After this meeting, an ultrasound is performed to determine the position of the baby and placenta, the number of babies, the gestational age and the fetal anatomy. Depending on the placement of the placenta, one of two approaches is used to obtain the chorionic villus sample. With the transcervical approach, the vagina is cleaned and held in an open position with the speculum, and a thin tube is gently inserted through the cervix to reach the chorionic tissue. With the transabdominal approach, a thin needle is inserted through the abdominal skin into the uterus and placenta. Ultrasound is used during this process to guide the physician. Using gentle suction, a very small amount of chorionic villi is removed.
Transabdominal CVS |
|
Transcervical CVS |
|
How accurate is CVS?
CVS is a reliable method of prenatal diagnosis. Genetic evaluation of chorionic villi provides a high degree of success and accuracy for the diagnosis of common chromosome abnormalities. Since the chorionic tissue and the fetus originate from the same fertilized cell, they are usually genetically identical.
However, in approximately 1 in 100 cases (1%) the sample shows a mixture of normal and abnormal cells. If this happens, a follow up amniocentesis may be indicated. There is a 1 in 1,000 chance that even though the CVS results are normal, the baby may have a chromosome abnormality. It is also possible that some maternal cells remain in the sample that the laboratory tests. If this happens, the results may reflect the mother's chromosomes rather than the babies.
Is CVS Safe?
CVS is a safe procedure with a risk of miscarriage (less than 1 in 100) being similar to genetic amniocentesis. When performed by a qualified Perinatologist, the risk for complications is much lower, with success rates from 97.8% to 99.4%.In addition, miscarriages can happen spontaneously, unrelated to the procedure, especially at this earlier gestational age. Some occasional side effects are vaginal spotting, cramping or leaking of fluid after the procedure. If these symptoms occur, they usually do not result in a miscarriage.
When will the results be ready?
Although it depends on the type of test, results are usually known between 7 and 14 days. The cells need to grow in a laboratory for a few days before any testing can be performed. In some instances, the results could be delayed because the cells grow slowly or the genetic testing takes longer than expected. After the results are known, a patient will be called with the information and a report will be sent to her physician.
How do I schedule a CVS?
CVS is performed by Jeffrey G. Boyle, MD or Peter Van Eerden, MD, Board Certified Maternal Fetal Medicine Specialists at Sanford Clinic, MFM. Consultation to discuss the procedure or appointments can be made by calling (605) 328-4600.
