Chorionic Villus Sampling
Chorionic Villus Sampling (CVS)
Uses
- sampling early during pregnancy allow for advanced knowledge of congenital defects, including:
- Down's syndrome
- cystic fibrosis
- Duchenne muscular dystrophy
- analysis of chromosome structure is not as detailed as with amniocentesis
Procedure
- done at or after 10 weeks after LMP
- usually takes 20-30 minutes
- performed by transabdominal or transcervical needle guided by ultrasound; transcervical is
- small fragments of chorionic villi: are drawn up and examined
- need tertirary villi from the chorion frondosum and are composed of the mesencymal core, cytotrophoblast and outer layer of syncyiotrophoblast
- direct analysis is performed on trophoblast cells, which due to their rapid proliferation can elad to increased mitotic error
- culture analysis examines the karyotype of cells from the mesenchymal core of the chorionic villi
Risks
- some risk of miscarrage due to damage to fetus; higher than with amniocentesis
- potential response in Rh -ve mothers to Rh +ve placenta
- potential risk of birth defects due to placental damage
- can sample mom too by mistake;
Patient Instructions