The heavy menstrual flow and stomach pain in the second month after the IUD is considered to be related to the side effects of the IUD and a history of menstrual cramps. 1. Side effects of IUD: IUD is a kind of uterine operation, and the heavy menstrual flow and stomach pain after IUD is considered to be related to the side effects of IUD. Patients mainly manifested as increased menstrual flow, prolonged menstrual period or irregular vaginal bleeding. It is recommended to observe closely and go to the gynecology department of the hospital for consultation if necessary. 2. History of dysmenorrhea: If there is a history of dysmenorrhea in the past, the primary problem still exists after IUD. Therefore, the symptoms of stomach pain will appear during menstruation. In addition to this, some women have stomach pain after IUD, which may be caused by mental stress or other factors. In addition, heavy menstrual periods and tummy pain may also occur if there is a secondary infection in the uterine cavity after IUD, and this kind of tummy pain usually exists during non-menstrual periods as well. For stomach pain and heavy menstruation after IUD, it is recommended to observe closely and go to the gynecology department of the hospital for examination if necessary to understand the cause.