Fig. 1

High-quality cleavage-stage embryo characteristics and flow diagram of retrospective study selection for blastocyst culture and embryo transfer. Phenotypes of high-quality cleavage-stage embryos examined by light microscopy. Scale bars 50 μm. (A) category ‘811’ was defined to include embryos with 8 cells and symmetrical stage-specific cell size and less than 10% fragmentation. (B) category ‘711’ was defined to include embryos with 7 cells and symmetrical stage-specific cell size and less than 10% fragmentation. (C) category ‘911’ was defined to include embryos with 9 cells and symmetrical stage-specific cell size and less than 10% fragmentation. (D) category ‘812’ was defined to include embryos with 8 cells and symmetrical stage-specific cell size and 10 − 25% fragmentation. The black arrowhead indicates fragmentation. (E) category ‘821’ was defined to include embryos with 8 cells and asymmetrical stage-specific cell size (the white circle and the blue circle) for minority of cells (1–2 cells) and less than 10% fragmentation. (F) Flow diagram of this study selection for blastocyst culture and embryo transfer of five groups