It is usually good that the endometrium falls out because it is shed every month from puberty to menopause, mainly because the endometrium is influenced by the ovaries’ cyclical secretion of estrogen and progesterone and is shed periodically, which is a normal physiological phenomenon of vaginal bleeding and menstruation. However, when menstruation occurs, the endometrium is discharged outside the vagina in the form of fragments, and if large pieces are discharged, it may lead to menstrual pain. In most cases, the endometrium is overactive or inflammation of the endometrium, which can cause large pieces of endometrium to fall out. In this case, it is recommended to find out the cause and give timely treatment if there is inflammation.