Understanding the molecular basis of endometrial receptivity is crucial for improving implantation outcomes in assisted reproduction, especially for patients with recurrent implantation failure (RIF). This study investigates the timing relationship between microRNA (miRNA) and messenger RNA (mRNA) profiles in the endometrium using simultaneously the endometrial receptivity array (ERA) and the microRNA receptivity assay (MIRA) in 100 RIF patients undergoing euploid blastocyst transfer. The concordance rate between ERA and MIRA was 72% (Kappa = 0.50), suggesting partial overlap in profiling. Patients were stratified by the timing sequence of miRNA relative to mRNA into Fast, Equal, and Slow groups. Those with delayed miRNA expression (Slow group) had significantly lower pregnancy rates (54.5%) than those with synchronous or leading miRNA expression (81.9% and 94.1%, respectively; p = 0.031). Moreover, the Slow group exhibited higher prior implantation failure counts and altered expression in 15 miRNAs, many involved in aging-related pathways. These findings highlight that asynchronous miRNA-mRNA profiles may reflect impaired receptivity and suggest that miRNA-based staging adds valuable diagnostic insight beyond mRNA profiling alone. Dual assessment of mRNA and miRNA profiles may offer additional diagnostic insight into endometrial receptivity but requires further validation before clinical application.
Keywords: embryo transfer timing; endometrial receptivity; messenger RNA; microRNA; recurrent implantation failure.