Molecular Factors Affecting Embryo Implantation: A Narrative Review

Background: Embryo implantation involves the interaction between the blastocyst and the host uterus that occurs over a limited period called the implantation window. Objective: The present study was conducted to investigate the factors involved in embryo implantation. Methods: In this review study, to review the effective factors in implantation, Persian and English articles from databases such as PubMed, Scopus, Science Direct, Google Scholar, and MagIran from 2000 to 2022 using the keywords of embryo implantation, effective factors in implantation and infertility were investigated. Results: Uterine receptivity for embryo implantation is regulated by the ovarian hormones estrogen and progesterone. Defects in the regulation of cytokine expression will lead to incomplete implantation failure. The potential role of growth factors such as leukemia inhibitory factor, interleukin-1, interleukin-6, interleukin-11, colony stimulating factor-1, epidermal growth factor family, and insulin-like factor in the important implantation process has been described. HOX genes are transcriptional regulators that play an essential role during embryonic development and continue to be expressed in the development of primary female reproductive tract tubes and then in the adult uterus. The role of morphogens in implantation has been proven and they are effective in embryo-uterine interactions during this process. Conclusion: Understanding the biology of implantation can reduce female infertility and help develop new therapies for fertility.