Decidualization is the differentiation of endometrial stromal cells into secretory decidual stromal cells. Human decidualization involves some amount of signaling molecules and pathways as well as genetic reprogramming, which is driven by the postovulatory rise in progesterone levels and local cyclic adenosine monophosphate production. Decidualization extends from the primary decidual zone to the secondary decidual zone, and then exits through apoptosis. Evidences support that decidual fibroblasts function as the pool of decidual stromal cells during pregnancy. Decidualization undergoes an acute inflammatory phase, an anti-inflammatory secretory phase to the final recession phase. The decidualization of the inner layer of endometrium, termed decidua, is the most critical determinant of pregnancy success, which can promote placenta formation, modulate immune tolerance, foster resistance to oxidative stress, sense embryo quality, and control labor. Failure to adequate decidualization in terms of hormones, biochemistry, and immunology leads to adverse pregnancy outcomes, including diseases such as preeclampsia, miscarriage, premature labor, repeated implantation failures, and some age-related decline in reproductive capacity. The development of animal models and in vitro culture systems combined with emerging technologies provides a powerful system to explore the mechanism of decidualization. However, decidualization is a dynamic, multi-step process, and translating of current research progress into disease predictions and interventions for pregnancy complications remains to be achieved. The study of periodic regeneration and spontaneous decidualization of the endometrium will be beneficial to the diagnosis and treatment of pregnancy diseases.

Decidualization is the differentiation of endometrial stromal cells into secretory decidual stromal cells. Human decidualization involves some amount of signaling molecules and pathways as well as genetic reprogramming, which is driven by the postovulatory rise in progesterone levels and local cyclic adenosine monophosphate production. Decidualization extends from the primary decidual zone to the secondary decidual zone, and then exits through apoptosis. Evidences support that decidual fibroblasts function as the pool of decidual stromal cells during pregnancy. Decidualization undergoes an acute inflammatory phase, an anti-inflammatory secretory phase to the final recession phase. The decidualization of the inner layer of endometrium, termed decidua, is the most critical determinant of pregnancy success, which can promote placenta formation, modulate immune tolerance, foster resistance to oxidative stress, sense embryo quality, and control labor. Failure to adequate decidualization in terms of hormones, biochemistry, and immunology leads to adverse pregnancy outcomes, including diseases such as preeclampsia, miscarriage, premature labor, repeated implantation failures, and some age-related decline in reproductive capacity. The development of animal models and in vitro culture systems combined with emerging technologies provides a powerful system to explore the mechanism of decidualization. However, decidualization is a dynamic, multi-step process, and translating of current research progress into disease predictions and interventions for pregnancy complications remains to be achieved. The study of periodic regeneration and spontaneous decidualization of the endometrium will be beneficial to the diagnosis and treatment of pregnancy diseases.