Russell JB, et al. - A retrospective cohort study is done to evaluate the endometrial biopsy (EB) findings with the transfer of a single euploid embryo with the ongoing pregnancy rate. The ability for any embryo to implant requires an in phase endometrium synchronized with the developmental stage of the embryo. As preimplantation genetically screened (PGS) improves their selection process assessing the endometrium of failed hormone replacement (HR) frozen embryo transfer (FET) cycles or prior to transfer may lead to improved pregnancy rates maximizing the benefits of PGS.