Chorionic villi sampling: laboratory experience with 4,000 consecutive cases

Experience with 4,000 consecutive CVS cases shows that 1) the combination of both the direct and culture methods greatly reduces false diagnoses and maternal cell contamination; 2) the time interval between the sampling procedure and processing of villus specimens influences the quality of direct preparations; 3) maternal cell contamination (MCC) can be minimized with dissection of CVS specimens. We have compiled a large volume of confined placental mosaicism (CPM) cases to serve as a resource in interpreting mosaic cytogenetic findings. It was noted that, in up to 92% of the mosaic cases, the abnormal cell line was confined to the placenta. The frequency of true chromosomal mosaicism was 0.2%, and is not different from that for amniocentesis.