Secretory Phase

During the secretory phase of the menstrual cycle, the endometrium becomes thicker and more vascularized and the endometrial glands become engored with secretions.

These changes are driven by progesterone from the corpus luteum and peak approaximately one week after ovulation.

Predecidualization also occurs, with stromal cells transforming into rounded decidual cells and spreading across the endometrial surface to form the zona compacta.

During pregnancy, decidualization is sustained and extended in preparation for implantation of the zygote.