Embryo implantation process

The embryo implantation process is a highly regulated, multi-phase event in which a blastocyst (early embryo) attaches to and invades the uterine endometrium, initiating pregnancy[1][2][4][5]. This process requires synchronized preparation of both embryo and endometrium, largely under the control of ovarian steroid hormones (estrogen and progesterone) and entails tightly regulated paracrine, autocrine, and juxtacrine molecular interactions[1][4][6]. Key phases include apposition, adhesion, and invasion of the endometrial lining by trophoblast cells. Multiple molecular mediators—such as steroid hormones, growth factors (e.g., HB-EGF), cytokines, adhesion molecules (e.g., L-selectin), and changes in endometrial gene/protein expression—govern this process[1][3][4][6]. The outcome is formation of the decidualized uterine tissue and subsequent placentation to support embryonic development[6][7].

Other names

ImplantationEmbryo implantationBlastocyst implantationNidation