No abstract

Among 3499 cytogenetically investigated semi‐direct chorionic villus samples, 219 (6·3 per cent) abnormal karyotypes were encountered. The karyotypes were considered certainly abnormal (generalized abnormal with high probability) in 109 cases (3·1 per cent), and in 110 cases (3·1 per cent) uncertainly abnormal (potentially confined to the placenta), requiring further investigation. Of these 110 uncertain abnormalities, the cytogenetic result turned out to be finally abnormal representing generalized abnormality in 36 cases (32·7 per cent), finally normal representing confined placental mosaicism (CPM) in 69 cases (62·7 per cent), and remained undetermined in 5 instances (4·5 per cent). The rate of the numbers of certainly abnormal and all (certainly+uncertainly) abnormal results, the certainty rate, and that of generalized abnormalities and all abnormalities (generalized abnormalities+CPM cases), the predictive value, are strongly correlated with the cytogenetic risk. Therefore, we advise chorionic villus sampling for cytogenetic investigation only in women with a cytogenetic risk equal to or exceeding that of a 40‐year‐old pregnant woman. Because of the high rate of prenatal follow‐up investigations after the finding of uncertain results in semi‐direct villi, semi‐direct and cultured villi should be karyotyped simultaneously. Copyright © 1998 John Wiley & Sons, Ltd.

In 3,000 chorionic villi studies (CVS) 33 cases of mosaicism and 7 false-positive cell lines in all cells were seen. The mosaic cell lines were caused by aneuploidy of autosomes (13x), sex chromosomes (9x), and structural anomalies (11x). Mosaics of fetal origin were only 4 cases of trisomy 21 and one 47,XXY mosaic. In 7 cases abnormal karyotype of non-fetal origin was seen in all cells in direct studies, including trisomy 16 (3x) and trisomy 18 (2x). The combined use of direct CVS and cell cultures always uncovered the non-fetal origin of chromosome abnormalities and the study of cultured cells in all cases could have prevented 5 terminations. Complete follow-up studies demonstrated no false-negative results. Therefore, CVS can be nearly 100% accurate when both direct studies and cultures are examined in cases of mosaicism and other cell lines of possible non-fetal origin, such as trisomy 16, trisomy 18, translocation (21;21), and 45,X cells.