Project description:Many studies estimate that chromosomal mosaicism within the cleavage stage human embryo is high. However, comparison of two unique methods of aneuploidy screening of blastomeres within the same embryo has not been conducted and may indicate whether mosaicism is overestimated due to technical inconsistency rather than biological phenomena. The present study investigates the prevalence of chromosomal abnormality and mosaicism found with two different single cell aneuploidy screening techniques.Thirteen arrested cleavage stage embryos were studied. Each was biopsied into individual cells (n=160). The cells from each embryo were randomized into two groups. Those destined for FISH based aneuploidy screening (n=75) were fixed, 1 cell per slide. Cells for SNP microarray based aneuploidy screening (n=85) were put into individual tubes. Microarray was significantly more reliable (96%) than FISH (83%) for providing an interpretable result (P=0.004). Markedly different results were obtained when comparing microarray and FISH results from individual embryos. Mosaicism was significantly less commonly observed by microarray (4 of 13 embryos; 31%) than by FISH (13 of 13 embryos; 100%)(P=0.0005). Although FISH evaluated fewer chromosomes per cell and fewer cells per embryo, FISH still displayed significantly more unique genetic diagnoses per embryo (3.2+0.2) than microarray (1.3+0.2)(P<0.0001). This is the first prospective, randomized, blinded, and paired comparison between microarray and FISH based aneuploidy screening. Aneuploidy and mosaicism were less common with microarray. While evaluating a smaller number of chromosomes with a proportionally smaller opportunity for finding mosaicism, FISH still had a dramatically higher level of inter-cell variation in diagnosis. SNP microarray based 24 chromosome aneuploidy screening provides more complete and consistent results than FISH.