BAX and cholesteryl ester measurement: Pietro et al. have reported that the abnormal expressions of inflammatory response factors and apoptosis-related factors, such as IL-11, chemokine ligand 4 (CCL4), insulin-like growth factor (IGF1), B cell CLL 2 (BCL2), and BCL2-associated X protein (BAX), within CE case endometria during implantation result in decreased endometrial receptivity, resulting in embryo implantation failures [12].