Which layers of the endometrium are shed during menstruation?

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Diagram of the menstrual cycle showing hormone levels, follicle development, and endometrial changes across 28 days. It highlights menstruation, ovulation, and the follicular and luteal phases, with labeled curves for estrogen, progesterone, FSH, and LH. — menstruation Cyclical changes during a woman's normal ovulatory menstrual cycle.

During menstruation, the inner two layers of the endometrium are shed. These layers are the stratum compactum and the stratum spongiosum.1

The third layer, known as the stratum basale, remains in position against the myometrium and serves as the foundation from which the endometrium regenerates during the next cycle.12