Under normal circumstances, intercourse will not affect menstruation, but intercourse during menstruation can affect menstruation. During menstruation, the endometrium sheds and intercourse will stimulate the uterus, resulting in increased menstrual flow and prolonged menstrual period. The body’s resistance decreases during menstruation when intercourse will bring bacteria into the uterus, it is easy for bacteria to breed and cause various gynecological inflammatory diseases, such as pelvic inflammatory disease, tubal inflammatory disease, etc., which can seriously affect normal fertility. It is also not good for men to have intercourse during their periods, as menstrual blood can easily cause bacteria to grow and cause male diseases. For the sake of health, it is important to avoid menstruation when having intercourse, otherwise it will affect your health. You can have intercourse three days after the end of your period when the uterus is closed and your body is more resistant to bacterial infections. However, we should pay attention to the hygiene of intercourse and wash before and after intercourse to reduce gynecological diseases.