It is not allowed to have sex during menstruation. Sex during menstruation may cause infection in the reproductive tract. Due to the presence of menstrual blood, it is easy to cause bacteria to multiply, and there is a large trauma after the endometrium is exfoliated which is easy to cause bacterial infection, and the immune function of women will change, leading to a decrease in resistance to disease, and also easy to cause endometriosis or infertility, dysmenorrhea, etc. The use of condoms by men during menstrual intercourse may cause inflammation or swelling of the vaginal opening due to reduced lubrication in the vagina due to blood. Orgasm during menstruation promotes uterine contraction, and engaging in sexual intercourse during the first half of menstruation may lead to increased menstrual flow. It is advisable to have sex after 3-7 days of menstruation and to use contraception to avoid unwanted pregnancy.