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Objective: We evaluated the effects of platforms, size filter cutoffs, and targeted regions of cytogenomic microarray (CMA) on the detection of copy number variants (CNVs) and uniparental disomy (UPD) in prenatal diagnosis., Methods: Five thousand twenty-six consecutive prenatal specimens (>98% high-risk pregnancy) were studied by high-resolution CMA, with cutoffs of 50 kb for losses and 200 kb for gains in nontargeted regions and 20 kb for losses and 100 kb for gains in targeted regions. We assessed actual detection rates using the current assay as well as hypothetical detection rates using platforms with the same or lower resolution and smaller or larger cutoffs., Results: The detection rate of our current assay was 11.2% (562 of 5026), including abnormal findings in 543 cases and likely pathogenic variants in 19. The hypothetical decrease in the overall detection of variants (excluding likely benign) and UPD ranged from 3.8% to 23.0%. For the subgroup of pathogenic and likely pathogenic CNVs < 1 Mb, the decrease of detection ranged from 2.7% to 24.3%., Conclusions: These findings underscore the significant effects of chosen CMA platform, as well as size filter cutoffs and targeted regions used in data analysis, on detection of CNVs and UPDs in a cohort of prenatal cases., (© 2019 John Wiley & Sons, Ltd.)

We report on the second trimester prenatal diagnosis of an apparently nonmosaic tetraploid fetus, 92,XXYY. Indications for cytogenetic studies of the fetus included abnormal ultrasound findings and abnormal maternal serum levels of alpha-fetoprotein (AFP)/estriol. Chromosome analysis of amniocytes documented tetraploidy, a finding confirmed by flow cytometry of several fetal tissues. Autopsy findings in the fetus are compared with those of other cases of tetraploidy. To our knowledge this is the first reported prenatal diagnosis of a tetraploid fetus. Additionally, it illustrates the value of flow cytometric analysis of products of conception in which polyploidy is suspected.