ABNORMAL KARYOTYPES IN SEMIDIRECT CHORIONIC VILLUS PREPARATIONS OF WOMEN WITH DIFFERENT CYTOGENETIC RISKS

Among 3499 cytogenetically investigated semi-direct chorionic villus s amples, 219 (6.3 per cent) abnormal karyotypes were encountered. The k aryotypes were considered certainly abnormal (generalized abnormal wit h 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 abnormalitie s, the cytogenetic result turned out to be finally abnormal representi ng 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 + uncerta inly) abnormal results, the certainly rate, and that of generalized ab normalities 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 i nvestigation only in women with a cytogenetic risk equal to or exceedi ng that of a 40-year-old pregnant woman. Because of the high rate of p renatal follow-up investigations after the finding of uncertain result s in semi-direct villi, semi-direct and cultured villi should be karyo typed simultaneously. (C) 1998 John Wiley & Sons, Ltd.