LAUSR

The endometrium is a hormonally regulated organ that is non-adhesive to embryos throughout most of the menstrual cycle in humans. Endometrial receptivity refers to a hormone-limited period in which the endometrial tissue acquires a functional and transient ovarian steroid-dependent status allowing blastocyst adhesion. Functional genomic studies of human endometrium in natural cycles have demonstrated that endometrial receptivity is an active process involving up- and down-regulation of hundreds of genes ( 1 ). Personalized medicine is a well-accepted concept in reproductive medicine except for the endometrial factor that is still neglected. Our group has developed the endometrial receptivity array (ERA) ( 2 ), a customized array of 238 genes now performed using Next Generation Sequencing (NGS) coupled to a computational predictor capable of diagnosing the window of endometrial receptivity regardless of its histological appearance ( 2 ). The accuracy of the diagnostic tool ERA has been demonstrated to be superior to endometrial histology and results are completely reproducible 29 to 40 months later ( 3 ). The aim of this presentation is to demonstrate the diagnostic and therapeutic efficiency of ERA in patients with implantation failure (IF), through personalization of the day of embryo transfer (pET) ( 4 , 5 , 6 , 7 , 8 ). We are conducting an international RCT to investigate the reproductive outcome of infertile women under 38 year (BMI of 18.5-30 and AFC>8) s in their first IVF/ICSI cycle with elective blastocyst transfer randomly allocated to be performed in a fresh cycle, after freezing all embryos or after identification of the personalized WOI with the ERA test (pET). According to a preliminary analysis after recruiting 356 patients of the 546 planned, the pET group had a higher pregnancy rate per ET, and a trend to a higher implantation rate and ongoing pregnancy rate ( 9 ). Finally, the investigation of endometrial bacterial communities has revealed that the endometrial cavity is not sterile. The presence of a Non-Lactobacillus-dominated microbiota (NLD) ( 10 ) or pathogens responsible for chronic endometritis ( 11 ) in infertile patients are associated with decrease reproductive outcome in terms of implantation, pregnancy and live birth rates.