Progesterone governs endometrial proliferation-differentiation switching and blastocyst implantation.

Blastocyst implantation contains the following three processes: apposition, attachment, and invasion of the blastocyst. Ovarian hormone progesterone (P) regulates these processes exquisitely. P-induced molecular communications between the endometrial epithelium and stroma as well as endometrial proliferation-differentiation switching (PDS) until blastocyst attachment are fundamental steps in blastocyst implantation. Based on the knowledge obtained from the previous studies of mouse models by my group and others, this article outlines how P directs the uterus to complete blastocyst implantation.