Genetics Northern California

Chorionic Villus Sampling

CVS is a procedure done to diagnose chromosome abnormalities during pregnancy. It is usually done between 10 weeks and 13 weeks 6 days of pregnancy. Ultrasound is used to guide the procedure. The test removes and analyzes a small sample of the developing placenta (chorionic villi).  Fetal chromosomes from the sample are studied in the laboratory.

 

CVS can be done in two different ways, either through the vagina and cervix (transcervical) or through your lower belly (transabdominal). The doctor decides which method will work best for each woman.

 

 CVS fact sheet:      Chorionic Villus Sampling.

Transabdominal CVS is done by inserting a thin needle through a woman's lower abdomen into the uterus and removing a small sample of the placental tissue (chorionic villi).

Transcervical CVS is done by inserting a thin flexible tube (catheter) through the vagina and cervix into the uterus and removing a small sample of the placental tissue (chorionic villi). 

Risks: The risk for miscarriage due to the CVS procedure is 1 in 500 or less.

Results: Results from CVS are usually available within 14 days. A genetic counselor calls you as soon as they are available. The results can accurately tell whether or not the baby has a chromosome abnormality, such as Down syndrome or trisomy 18. The result is unclear in about 3-5% of CVS tests. More testing may be recommended. 

CVS does not detect neural tube defects (NTDs).  This type of birth defect can be found by a screening test and ultrasound between 15 and 20 weeks of pregnancy.  

Last reviewed:   April 2020

Reviewed by:  Kimberly Barr, LCGC, Kaiser Permanente NCAL Genetics