Women with blood clots during menstruation may be due to physiological reasons, such as a large amount of shedding of the uterine lining; they may also be due to pathological reasons, such as uterine fibroids, endometrial lesions and so on. 1. Physiological reasons: menstrual blood consists of shed endometrium, cervical mucus, blood and vaginal epithelial cells, when the bleeding is heavy and fast, and the shedding of endometrium is too much, the phenomenon of blood clots may occur. 2. Pathological causes: (1) Uterine fibroids: If uterine fibroids are present, due to the increased area of the endometrium and the poor contraction of the myometrium, etc., they may be manifested in symptoms such as heavy menstruation, blood clots, and also prolongation of the menstrual period. (2) Endometrial lesions: If endometritis, endometrial polyps and other diseases exist, they can also manifest as increased menstrual flow with blood clots. Women with blood clots during menstruation are advised to consult a doctor in time, complete the relevant examinations, and receive targeted treatment under the guidance of a specialist.