Chorionic Villus Sampling: Is it Safe?

Are you considering having the chorionic villus sampling test (CVS) performed but you're worried about the possibility of miscarriage? Making the decision is tough, but having the facts on hand can help you make the right choice.

Diagnostic Test

Studies performed in the 1980's just after CVS became available, suggested that there is a slight increase in miscarriages after CVS as compared to the number of miscarriages occurring after amniocentesis. Amniocentesis is a diagnostic test which, like CVS, can rule out specific birth defects. The difference between the two tests is in the timing. CVS is performed between the 10th and 12th weeks of pregnancy, whereas amniocentesis can only be performed between the 15th and 20th weeks of pregnancy. Health care providers tell women that the risk of miscarriage posed by CVS stands at about 1% or 1 in every 100 cases as opposed to 0.5 % or 1 miscarriage in every 200 cases for amniocentesis.

The fact is, however, that doctors have gained much experience in performing CVS and the risk appears to be much lower than the commonly cited figure. More recent studies show little difference in the rate of miscarriage between the two procedures, amniocentesis and CVS, when performed by experienced physicians. Research conducted in 2006 by the University of California, in San Francisco, demonstrated that the rate of miscarriage was 1 in 360 for CVS as compared to 1 in 370 for amniocentesis. The gap between these two numbers is not considered statistically significant.

Similar Risk

The lowest risk for miscarriage after CVS is associated with facilities in which both types of CVS procedures, transcervical and transabdominal, can be performed, which means that the option deemed safest for a particular patient will always be available. Studies suggest that the rates of miscarriage for both procedures are the same.

Back in the early 1990's concerns related to CVS surfaced after many reports of infants born with missing or foreshortened digits, in some cases with accompanying abnormalities of the tongue and lower jaw. Because these birth defects were seen when CVS was performed earlier than the 10th week after the mother's last menstrual period, it was decided the procedure would no longer be performed before the 10th week. More recent surveys confirm that limb defects are not seen when CVS is performed between the 10th and 12th week after the last menstrual period.