Abstract: ABSTRACT Objective: To evaluate the aneuploidy status of chromosome X, Y and 18 in day 3 cleavage stage embryos with low morphological scores by the fluorescent in situ hybridization. Methods: The discarded embryos from IVF-ET cycles were collected for our research. Nuclei of all the blastomeres were fixed in which the chromosome X, Y and 18 were analyzed by FISH. Results: Fluorescent signals were successfully detected in 233 nuclei, in which 115 (49.4%) nuclei were normal euploidy of chromosome X, Y and 18, while 118 (50.6%) were abnormal. The aneuploidy rate of chromosome 18 and X/Y were 40.8% and 33.5% respectively, but the differences was not statistical significant. The trisome rate of chromosome 18 was statistical higher than that of chromosome X/Y (21.9%vs.12.0%, P<0.01). Conclusion: A majority of the day 3 cleavage stage embryos with low morphological scores were proved to be chromosomal abnormal. The general embryo morphology scoring criteria could predict the embryo euploidy status to some extent.

Key words: Aneuploidy, Fluorescence in situ hybridization, Cleavage stage embryo Embryo, morphology scoring