The secretory phase refers to the increased secretory activity by glands in the endometrium. The increased secretory activity in this phase of menstruation creates an ideal environment in the uterus for implantation of the blastocyst if fertilisation should take place. The secretory phase typically lasts about 13 days, and coincides with the formation, function and growth of the corpus luteum in the ovarian cycle.

For more information, see Menstruation.