Chorionic Villus Sampling (CVS)

What is chorionic villus sampling (CVS)?

Chorionic villus sampling (CVS) is a prenatal test that involves taking a sample of some of the placental tissue. This tissue contains the same genetic material as the fetus and can be tested for chromosomal abnormalities and some other genetic problems. Testing is available for other genetic defects and disorders depending on the family history and availability of laboratory testing at the time of the procedure.

How is chorionic villus sampling performed?

CVS may be offered to women who are at increased risk for chromosomal abnormalities or have a family history of a genetic defect that is testable from the placental tissue. CVS is usually performed between the 10th and 12th weeks of pregnancy. Although exact methods can vary, the procedure involves inserting a small tube called a catheter through a woman's vagina and into her cervix. the procedure follows this process:

• Ultrasound is used to guide the catheter into place near the placenta.
• Tissue is removed using a syringe on the other end of the catheter.
• Another method is transabdominal CVS, which involves inserting a needle through the woman's abdomen and into her uterus to sample the placental cells.
• Women may feel some cramping during and after the CVS procedure.
• The tissue samples are sent to a genetic laboratory to grow and be analyzed. Results are usually available in about 10 days to two weeks, depending on the laboratory.

Women with twins or other multiples usually need sampling from each placenta. However, because of the complexity of the procedure, and positioning of the placentas, CVS is not always feasible or successful with multiples. Some women may not be candidates for CVS or may not obtain results that are 100 percent accurate, and may, therefore, require a follow-up amniocentesis. In some cases, there is an active vaginal infection such as herpes or gonorrhea, which will prohibit the procedure. Other times, the doctor obtains a sample that does not have enough tissue to grow in the laboratory, such that results are incomplete or inconclusive.

Maternal and Fetal Testing

The vast majority of women have healthy pregnancies and their babies are born without difficulties. However, women with high-risk pregnancies often need a close watch for potential problems or complications. Fortunately, there are many tests and procedures to monitor the health of both mother and baby. Many of these pose little or no risk and can provide tremendous amounts of information to doctors, midwives, and expectant parents. Some types of testing and procedures, however, do carry some risks to mother, baby, or both.