The disadvantages of intercourse during menstruation are the following: 1. It can cause infection of the reproductive tract. During menstruation, the endometrium is not yet repaired, so if you have intercourse, pathogenic bacteria will easily infect the endometrium and cause inflammation of the endometrium. 2. Intercourse during menstruation is likely to cause damage to the vaginal mucosa and the cervical mucosa. Because during menstruation, the vaginal mucosa and cervical mucosa are in a congested state. If you have intercourse, it will cause damage to the local mucous membrane and cause tissue damage, resulting in local inflammation. 3. Intercourse during menstruation can also cause endometriosis and dysmenorrhea, which can even lead to infertility.