decidualized

Decidualized refers to tissues or cells that have undergone decidualization, a transformation of the endometrium in preparation for and during pregnancy. In humans, the process is driven largely by progesterone after ovulation and is enhanced by signals from the conceptus after implantation. The endometrial stromal cells enlarge and acquire a specialized secretory phenotype, becoming decidual cells that support embryo implantation and growth.

During decidualization, stromal cells accumulate glycogen and lipid droplets, change shape, and express specific proteins such as IGFBP-1 and members of the prolactin family. The endometrium becomes a decidua, with functional subdivisions including the decidua basalis at the site of implantation, the decidua parietalis lining the uterine cavity, and the decidua capsularis covering the conceptus as it expands. The decidua both nourishes the embryo and helps regulate the maternal immune response to allow tolerance of the fetus.

Functions of a decidualized endometrium include providing a supportive matrix and secreted factors for placental development, remodeling maternal spiral arteries to improve blood flow, and producing immune-modulating signals that limit harmful inflammatory responses. Decidualization is essential for successful implantation and pregnancy maintenance; inadequate decidualization has been linked with infertility, recurrent pregnancy loss, and certain pregnancy complications such as preeclampsia.

Across species, decidualization can vary. In humans it occurs as a spontaneous, progesterone-driven change in the secretory endometrium, whereas other mammals may exhibit different or embryo-triggered patterns of decidual transformation.