Decidualization

Micrograph showing decidualization of the endometrium due to exogenous progesterone (oral contraceptive pill). H&E stain.

Decidualization is a process that occurs in early pregnancy. It is an adaption of the uterus to enable implantation of the embryo. It is also one of the consequences of oral contraception, preventing pregnancy.

In preimplantation physiology, decidualization is the process in the late secretory phase by which the endometrial stroma transforms itself into a dense cellular matrix. It is induced by progesterone secreted by corpus luteum. The result is the formation of a decidua. The purpose of the decidua is to impede the invasion of trophoblasts, a feat it accomplishes not only by forming the physical barrier but also by generating cytokines promoting attachment of the trophoblast.