During which phase of the menstrual cycle does the endometrium shed?

Menstrual phase

Reason — The shedding of the endometrium occurs when fertilisation does not take place, leading to menstruation. This happens during the menstrual phase. In the follicular phase, Follicle Stimulating Hormone stimulates the growth of ovarian follicles. In the ovulatory phase, the mature ovum is released from the ovary. In the luteal phase, after ovulation, the empty follicle becomes the corpus luteum, which releases progesterone and maintains the uterine lining for possible pregnancy. If fertilisation does not occur, the lining breaks down at the end of this phase.