The effect of endometrial injury on pregnancy rate in frozen-thawed embryo transfer: A randomized control trial

Abstract

Implantation failure is one of the most important factors limiting success in IVF treatment (1). Embryo implantation is a critical process of embryonic attachment to endometrium and subsequent invasion into uterine wall (2). Uterus is receptive during mid-secretory phase (days 19-23) of menstrual cycle, which is known as window of implantation (2). Implantation of embryo is a multiple process including several cytokines and growth factors, along with a dialogue between embryo and uterine endometrium (3). Numerous factors have been contributed increasing embryo implantation success (4). Majority of trials have demonstrated favorable effect of endometrial injury on implantation success rate, especially in women with recurrent implantation failure (RIF), while some studies failed to detect any benefit (5-13). Kalma et al suggested that “local injury to endometrium causes significant changes in pattern of expression of genes related to implantation” (14). Gnainsky et al reported that “endometrial injury induces an inflammatory reaction which favors implantation” (15). Dendritic cells, natural killer cells and macrophages are employed to local injury and increased amounts of cytokines, chemokines and growth factors are secreted, thus resulting in successful implantation (15, 16). To our knowledge, there has not been enough research due to the effectiveness of endometrial injury prior to frozen-thawed embryo transfer (FET) cycle. The purpose of our trial was to explore whether endometrial injury in luteal phase prior to FET cycle would improve pregnancy outcomes?