Clinical aspects of decidualization

An essential component of successful conception and pregnancy is decidualization, which involves structural and functional transformation of the endometrium. The process involves structural changes in the uterine mucosa, trans- formation of spiral arterioles, numerical and functional adaptation of leukocytes in the endometrium and their sub- sequent migration, and functional and morphological changes in decidual stromal cells. As part of decidualization, trophoblast cells of embryonic origin perform a physiological invasion of maternal tissue to create the placenta. The success of the process is due to the special antigenicity of the trophoblast cells and the immune communication be- tween the graft (fetus) and the host (mother) through hormones, cytokines and multiple receptor-ligand connec- tions. Disorders of these processes are the basis of several diseases that threaten conception, implantation, and suc- cessful pregnancy, such as recurrent miscarriage, preeclampsia, intrauterine retardation, or preterm birth. In this article, we review the anatomical, immunological, and molecular basis of physiological decidualization to address common disorders in the clinical practice of obstetrics that are related to a dysfunctional decidualization.