Chorionic Villus Sampling

Description

A technique for obtaining fetal chorionic villus cells for cytogenetic or other testing, chorionic villus sampling (CVS) is usually performed between 10 and 13 weeks gestation and involves the aspiration of the placental tissue using either percutaneous transabdominal or transcervical approaches. Transabdominal CVS can be performed at more than 13 weeks gestation. A transvaginal approach similar to the transabdominal method also has been used for retroverted uteruses. Results from CVS have a higher diagnostic uncertainty (confined placental mosaicism) than those from amniocentesis, and the procedure is associated with slightly more complications than second-trimester amniocentesis. The ability to obtain results earlier in pregnancy is important if termination based on findings is an option being considered.

Indications

Genetic testing for fetal chromosome anomalies prompted by risk factors, parental genetic screening, or an abnormal screening test result during the first trimester. Neural tube defects in the fetus cannot be detected by CVS.

Contraindications

Thrombocytopenia or antiplatelet antibodies, active vaginal bleeding, or infection are relative contraindications. For transcervical CVS: cervical stenosis, cervical or lower uterine myomas. For transabdominal CVS: Fetal position that blocks access to the placenta, known or suspected intraabdominal adhesions that could block access to the uterus. CVS may be technically difficult to accomplish in patients with multiple gestations. The risk for human immunodeficiency virus (HIV) vertical transmission associated with early invasive diagnostic techniques is lower than previously expected (3%) and similar to that in women who do not undergo the procedure.

Required Equipment

• Skin (or vaginal) preparation materials (iodine- or hexachlorophene-based antibacterial solution or other suitable cleansing agents)

• Sterile gloves

• Tissue transport medium (to be specified by the laboratory used and the test to be performed)

• Ultrasonography unit