Is it safe to have protected sex on the last day of menstruation?

Generally, it is not recommended to have protected sex on the last day of menstruation, as it may lead to infections.

Although menstrual flow tends to decrease on the final day, the cervix in women remains slightly open and the vaginal mucosal barrier function is still relatively weak. While using a condom can help reduce pathogen invasion, sexual intercourse during this time may still cause irritation due to friction, and may allow vaginal secretions or endometrial debris to travel upward into the urinary tract, potentially causing urinary or even reproductive system infections such as endometritis, pelvic inflammatory disease, or urethritis, which can negatively affect women's health.

About three days after menstruation ends, a woman’s body gradually returns to normal physiological function, and the risk of infection during intercourse at this time is significantly lower.