If a woman has sex when her period is not completely clean, it is easy for bacteria and other upward infections to occur, leading to the emergence of pelvic inflammatory disease. During menstruation, the capillaries in the uterus are in an open state, the body is easily fatigued, and the immunity is relatively poor at this time. Bacterial infections can easily occur, and if you have sex at this time, the microorganisms on the penis may reach the pelvis through the cervix, leading to local inflammation, manifested as abdominal pain, increased bleeding and so on. It is recommended that women do not have sex during menstruation. Sex at this time may also cause the shed endometrium to become ectopic, increasing the risk of endometriosis. If pelvic inflammatory disease occurs after sex, it is recommended to go to the hospital in time, under the guidance of the doctor for standardized treatment, to prevent the condition from worsening.