DISCREPANT KARYOTYPES AFTER 2ND-TRIMESTER AND 3RD-TRIMESTER COMBINED PLACENTACENTESIS AMNIOCENTESIS

Cytogenetic data are presented from a total of 1306 consecutive pregna ncies with successful diagnosis obtained from both chorionic villi aft er short-time culture (CVS-SC) and amniotic fluid cell cultures (AC); samples had been taken simultaneously at combined placentacentesis (pl acental biopsy) and amniocentesis during the second (92.8 Per cent) an d third (7.2 per cent) trimesters. Concordant results were obtained in 1218 pregnancies with a normal karyotype and in 62 pregnancies with a n aberrant fetal karyotype. Discrepant, i.e. false-positive and false- negative, results were found in 26 cases (2 per cent). From these data the accuracy of CVS-SC, defined as the proportion of all correct diag noses, is calculated to be 98 per cent. Three non-mosaic and 14 mosaic false-positive results obtained after CVS-SC could not be confirmed b y AC. Related to 1235 true normal fetal karyotypes, the specificity of CVS-SC, i.e. the proportion of normal karyotypes correctly diagnosed, amounts to 98.6 per cent. In nine pregnancies, an aberrant fetal kary otype detected after AC was missed by CVS-SC. The sensitivity of CVS-S C, i.e. the proportion of abnormal fetuses correctly diagnosed (62 out of 71), amounts to 87.3 per cent in our study group.