In the vast majority of cases, a woman’s endometrial lining will be about 10-12 mm thick before she has her period. However, the thickness of the endometrium at the time of menstruation varies from woman to woman because each woman’s specific situation is different, as well as hormonal secretion. For women who have had multiple abortions to terminate their pregnancy, the endometrium may be thinner before menstruation because the abortion may damage the endometrium, usually around 8 mm, or 7-9 mm in some cases, while some women may have a significantly thicker endometrium, usually around 14 mm, at the time of menstruation due to strong estrogen and progesterone secretion or incomplete endometrial peeling. 14mm or so.