Introduction: Frozen-thawed embryo transfer (FET) is a widely used technique, with replacement of embryos during natural menstrual cycles or in cycles constructed by exogenous steroids having similar outcomes in many series. Multiple factors have been proposed to have a positive influence on the success rate of FET, including increased endometrial thickness, younger maternal age and lower circulating oestradiol. The impact of these variables in the context of constructed cycles, using GnRH agonists to facilitate suppression of ovarian function prior to exogenous steroid administration, is not known. The aim of this study was to determine the predictive ability of these indices on clinical outcomes.