Chorionic Villus Sampling (CVS)
In this procedure, a
catheter is passed via the vagina through the
cervix and into the uterus to the developing
placenta under ultrasound guidance. Alternative approaches are transvaginal and transabdominal. The introduction of the catheter allows sampling of cells from the placental chorionic villi. These cells can then be analyzed by a variety of techniques. The most common test employed on cells obtained by CVS is
chromosome analysis to determine the karyotype of the fetus. The cells can also be grown in culture for biochemical or molecular biologic analysis. CVS can be safely performed between 9.5 and 12.5 weeks gestation. CVS has the disadvantage of being an invasive procedure, and it has a small but significant rate of morbidity for the
fetus; this loss rate is about 0.5 to 1% higher than for women undergoing
amniocentesis. Rarely, CVS can be associated with limb defects in the fetus. The possibility of maternal Rh sensitization is present. There is also the possibility that maternal blood cells in the developing placenta will be sampled instead of fetal cells and confound
chromosome analysis.
Please check out
Prenatal Diagnosis Overview
Ultrasound in PN Diagnosis
Amniocentesis
Maternal blood sampling for fetal blood cells