When a woman has endometriosis, she rarely experiences pain outside of her menstrual period, except in specific circumstances, such as during intercourse, where contact might be made with the ectopic endometrial lesions, causing severe pain, also known as dyspareunia. During menstruation, because the ectopic endometrial tissue is still active, it can undergo congestion, edema, rupture, and bleeding, leading to severe dysmenorrhea. Additionally, during the menstrual period, it can also cause an increase in prostaglandin secretion within the uterine cavity, enhancing the uterus's excitability, leading to dysmenorrhea.