Chorionic villus sampling (CVS) is a procedure that may be performed during pregnancy to diagnose certain genetic or chromosomal disorders. CVS involves having a biopsy of the developing placenta. The chorionic villi are the tiny units that make up the placenta and have the same genetic make-up as the fetus.
More detailed information about chorionic villus sampling is available by subscription. (See "Chorionic villus sampling".)
WHY IS CVS DONE?
CVS can test for a variety of genetic conditions, such as Down syndrome, Tay Sachs disease, and cystic fibrosis. It is generally performed during the first trimester of pregnancy, at 10 to 12 weeks, and the results are available within a few days.
Amniocentesis can provide similar information, but it can only be done later in pregnancy (typically at 15 to 17 weeks). (See "Patient information: Amniocentesis (Beyond the Basics)".)
Your healthcare provider may recommend CVS if:
- You have a family history of a genetic disorder
- You and your husband are carriers for genetic disorders, such as fragile X, Tay Sachs disease, or cystic fibrosis.
- Prenatal screening tests (blood tests or ultrasound) show that your fetus is at increased risk of having a genetic disorder.
CVS or amniocentesis? — CVS provides results in the first trimester. However, the procedure has a slightly higher risk of miscarriage compared to amniocentesis.
You may want to know if your fetus has a genetic disorder early in your pregnancy for several reasons:
CHORIONIC VILLUS SAMPLING PROCEDURE
There are two ways to perform CVS: through the cervix (called transcervical) and through the abdomen (transabdominal). The choice is based largely on where the placenta is attached to the uterus. With both methods, the procedure is performed while having an ultrasound.
Transcervical CVS — In the transcervical CVS technique, the physician inserts a small tube through the cervix into the placenta. This is done while ultrasound guides the physician (figure 1).
Transabdominal CVS — In the transabdominal CVS technique, the physician inserts a needle through the abdomen into the placenta. This is also done with ultrasound to guide the physician (figure 2).
The physician can usually obtain enough placental tissue the first time he or she inserts the needle or tube into the placenta. However, if there is not enough tissue, the physician may need to try again.
CHORIONIC VILLUS SAMPLING COMPLICATIONS
The most serious complication of CVS is miscarriage. CVS does not increase the risk of the fetus dying later in the pregnancy or after birth.
Miscarriage — Miscarriage can happen in any pregnancy. However, the risk of miscarriage is nearly 3 percent higher in women who have CVS compared to those who choose amniocentesis for prenatal diagnosis. Most of the risk is confined to transcervical amniocentesis, which carries a 3.5 percent greater risk of fetal loss than amniocentesis. Transabdominal CVS appears to carry a fetal loss rate similar to that of amniocentesis, with a pregnancy loss rate of 0.7 percent within 14 days and of 1.3 percent within 30 days . Amniocentesis can also cause miscarriage, although the risk is lower than with CVS.
Bleeding — It is normal to have some vaginal spotting after CVS. If you have heavier bleeding (eg, like a menstrual period), call your healthcare provider.
CVS can cause small amounts of fetal blood to be released into your bloodstream. This can potentially cause complications in future pregnancies, especially if you have an Rh negative blood type (eg, O negative). If you have an Rh negative blood type, you will be given Rhogam (Rh(D) immune globulin) after the procedure to prevent this complication.
Repeat testing — Some women who have a CVS will need a repeat CVS or amniocentesis. This can happen if the results of your first test are unclear, if the cells do not grow in the laboratory, or if there was not enough tissue collected.
WHERE TO GET MORE INFORMATION
Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient information: Chorionic villus sampling (The Basics)
Patient information: Should I have a screening test for Down syndrome during pregnancy? (The Basics)
Patient information: Amniocentesis (The Basics)
Patient information: Prenatal care (The Basics)
Patient information: Pregnancy in Rh-negative women (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Amniocentesis (Beyond the Basics)
Patient information: Abortion (pregnancy termination) (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Basic principles of genetic counseling for the obstetrical provider
Chorionic villus sampling
First trimester combined test and integrated tests for screening for Down syndrome and trisomy 18
Fetal blood sampling
The following organizations also provide reliable health information.
- National Library of Medicine