Abstract: In-vitro fertilization-embryo transfer（IVF-ET） is one of the most effective therapies for human infertility. However, the low implantation rate is still one of the clinical problems. The factors related to the rate of embryo implantation are from two aspects, factors of embryo quality and factors of endometrial receptivity. In this review, we discuss the new methods of selecting high-quality embryos such as time-lapse and pre-implantation genetic screening, as well as the endometrial receptivity and window of implantation.

Key words: Fertilization in vitro, Embryo transfer, Embryo implantation, Preimplantation diagnosis