Assessment of the early risks of chorionic villus sampling.

A study was carried out to develop proficiency in performing chorionic villus sampling (CVS) and to determine whether the risk for miscarriage was so high as to preclude a randomized clinical trial comparing CVS with amniocentesis. A total of 202 women who had decided to have induced abortions volunteered to either undergo CVS (101 women) or be a control (101). There were no differences between the two groups in factors that may affect the rate of miscarriage. CVS was performed an average of 9.8 days before abortion. The rate of fetal loss was significantly higher in the CVS group (p = 0.009). An analysis of the results as a function of the physician's experience over time showed that there were distinct learning phases. It may take longer than is generally recognized to acquire the expertise necessary to perform CVS with the lowest risk possible. Caution should be exercised before diagnostic CVS is offered to women who plan to continue their pregnancies.