How is a CVS done?
What will results tell me?
Risks and problems associated with CVS
CVS vs Amnio
A 'chorionic villus sampling' (or CVS) is a test that takes a small sample of cells from the baby's
placenta. The sample of cells is sent to the laboratory to 'grow' or 'culture', until there are enough cells that can be used to 'map' the baby's genes or chromosomes. A CVS aims to identify the presence of a genetic disorder (such as Down syndrome) or other inherited disorders such as muscular dystrophy or
cystic fibrosis. Even though a CVS is thought to be fairly accurate (up to 99%), not all birth defects and health problems can be detected with this procedure.
A CVS is usually performed between 10 and 12 weeks of pregnancy. This is earlier than an
amniocentesis, which is usually done at around 15 weeks of pregnancy.
How is a CVS done?
A CVS can be done two ways, vaginally through the
cervix (called 'transcervical' or 'TC') or through a needle inserted through the woman's abdomen into her uterus (called 'transabdominal' or 'TA'). The method that is used will often depend on the caregiver's preferences and the method they have most experience in. However, it may also depend on the position of the woman's uterus and where the baby's placenta is lying. If the placenta is low and posterior (lying towards the back of the uterus, closer to the woman's backbone) a vaginal CVS may be preferred. But if the woman's uterus is
retroverted (or 'tipped) and the placenta is anterior (lying at the front of the uterus, closer the woman's belly) then an abdominal CVS would probably be preferred.
Vaginal CVS was initially the only way a CVS could be performed. However, abdominal CVS had been available since the early 1990's and is now becoming the more preferred method, if possible. Both vaginal and abdominal CVS use an ultrasound (with the transducer placed on the woman's abdomen) to create an image of the baby and the placenta.