Causes and Treatment of Implantation Failure

In recent years, a high fertilization rate has been achieved via the rapid evolution of assisted reproductive technology. However, the overall pregnancy rate remains the same. Implantation failure appears to be one factor. In preparation for implantation, the human endometrium undergoes dramatic proliferation and differentiation during the menstrual cycle in response to the rise and fall of ovarian steroids. The characteristic restructuring of the endometrium is thought to be effected not only by steroids but also by locally released factors. Elucidation of the implantation mechanism and treatment of implantation failure may improve the low pregnancy rate in in vitro fertilization-embryo transfer. In this review, the cause of and treatment for implantation failure are summarized.