High-resolution chromosome analysis: I. Applications and limitations.

High-resolution chromosome preparations were examined in 55 couples experiencing multiple spontaneous abortions to determine if such studies might provide additional cytogenetic information. One translocation [46,XY,t(14;18) (q32; q22.2)] was detected that was not observed on routine metaphase preparations (GTG banding). In addition, an abnormality (not from the original sample) suspected on routine analysis was accurately identified as [46,XY, dir ins (12;21) (p12.3;q22.-1q22.2)] only after high-resolution studies. Metaphases with a total of 500-650 discernible bands per haploid set are most informative for high-resolution analysis of a complete karyotype. Chromosomes yielding this number of bands demonstrate 6.7-14.2% homolog discordance and usually require only three to five karyotypes to reach a diagnosis. GTG proved more effective than RBG banding in conjunction with high-resolution studies.