Decidualization
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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 by which the endometrial stroma transforms itself into a dense cellular matrix. It is induced by progesterone. 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.