Decidualization

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

Decidualization is a characteristic of the endometrium of the pregnant uterus. It is a response of maternal cells to progesterone. Decidualization may be used to describe any change due to progesterone. These changes include the eosinophilic proliferation around arterioles after ovulation^[1] or progesterone action on endometrium which increases glandular epithelial secretion, stimulates glycogen accumulation in stromal cell cytoplasm, and promotes stromal vascularity (spiral arterioles) and edema ^[2]. The sum of all the changes in the endometrium is significant, thus justifying a new term. The process is decidualization, the endometrium is now called decidua and it is ready for the implantation of the embryo.

After ovulation, in mammals, the endometrial lining becomes transformed into a secretory lining in preparation of accepting the embryo. Without implantation, the secretory lining will be absorbed (estrous cycle) or shed (menstrual cycle).

With implantation the lining now termed decidua evolves further during the pregnancy. The decidua is shed during the third phase of the parturition process.

References

1. ^ Lange Q&A, obstetrics and gynecology 8th edition, question 11 chapter 2, histology and pathology
2. ^ Lange Q&A, obstetrics and gynecology 8th edition, question 50 chapter 5, physiology of reproduction