Chorionic villi sampling (CVS) is indicated to determine if your child has a chromosomal disorder such as Tay-Sachs, sickle-cell anemia, most types of cystic fibrosis and Down syndrome.

• Trans-abdominal
• Trans-cervical

A small needle or catheter is introduced either through the abdomen "Transabdominal" or through the vagina/neck of the womb"  " Transcervical" into the uterus in order to collect a small sample of placental tissue called chorionic villi.

Ultrasound is used at the same time in order to guide the needle or catheter away from the baby.

Diagnostic study is performed on the cells in the sample 'as they are of fetal origin' to generate a detailed picture of the genetic makeup of the developing fetus.

In most  circumstances, the results from the test are available within three to five days.

Between 10th and 13th weeks of pregnancy.

Benefits

Chorionic villus sampling is reliable. The primary advantage of CVS is that results are available much earlier in pregnancy than amniocentesis which is done after 15 weeks. Thus, if results are abnormal, simpler and safer methods can be used to terminate the pregnancy, or the fetus can be treated prenatally. Also, normal result reduces parental anxiety earlier.

Risks

CVS is slightly riskier than amniocentesis. Miscarriage rate is 2% for transabdominal and 4% for transcervical. There are also some studies that suggest that there may be a slight increase in the number of limb deformities particularly if it is done earlier than 10 weeks. According to most studies, however, inexperience of the technician performing the procedure appears to be the cause of these rare complications.

Balancing the benefits and Risks

The risks have to be weighed against this benefit of earlier diagnosis and should be discussed at length with your doctor. If a genetic disorder is detected, you will be referred to a genetic counselor for further counseling and decision-making.