Results and pitfalls in prenatal cytogenetic diagnosis

Since 1969, the authors have cultured over 200 diagnostic amniotic fluids. Of these, 183 were for cytogenetic diagnosis. The chromosome analysis was successful in 168 cases. The indications and the results of the affected fetuses (followed by therapeutic abortion) are: (1) previous child with Down's syndrome: 62 cases (1:47,XX,+21); (2) advanced maternal age; 54 cases (1:47,XXY; 1:45,X/46,XY mosaicism; 1:47,+18); (3) previous child with multiple anomalies: 12 cases; (4) previous child with 47,XY,+18 or 47,+18 or 47,+13; five cases; (5) translocation carrier: two cases; (6) parental mosaicism: three cases; (7) X linked disorders: six cases (3:XY); (8) others: 24 cases. Firstly, it was found that for prenatal sex determination, karyotype analysis of the cultured amniotic fluid cells is the only accurate means and that caution must be taken if sex chromatin and Y fluorescent body determination from the uncultured amniotic fluid cells is used. Secondly, diagnosis of chromosomal mosaicism can be problematic as exemplified by the case of 45,X/46,XY mosaicism, where only 45,X cells were recovered from the first culture. Thirdly, in cases with enlarged satellites, cells of late prophase or early metaphase must be used to eliminate confusion with translocations. Three cases of enlarged satellites were encountered, one in the D group and two in the G group, and all three resulted in normal infants. Fourthly, the karyotype may be altered by contamination and/or treatment or other unknown factors. Two such cases where each mother delivered a normal infant were observed.