During menstruation, there are blood clots and fleshy substances, which are caused by the following reasons: 1. Considering that it is the cyclic shedding of the endometrium during menstruation, the blood contains a lot of substances, such as tissue lining, blood and vaginal secretions, etc., which may appear after the formation of clots, which is a normal bodily reaction; 2. It may be triggered by other diseases, such as tumors, and may lead to the production of blood clots and fleshy substances if the necrotic shedding of fibroids occurs in the uterine mucosa. It may be caused by other diseases, such as tumor diseases, if the uterine mucosa has necrosis and detachment of leiomyosarcoma, which may lead to the production of blood clots and fleshy material. It is recommended to carry out cancer screening in time to avoid the disease from becoming more serious; 3. It may be caused by endometriosis or other gynecological diseases, and it is recommended to carry out examination and treatment in time, and the meaty tissues in the blood can be screened pathologically, and then a clear diagnosis can be made.