1.Because of the excitement of both sides, penile penetration will make female genitalia engorged with blood, resulting in increased menstrual flow and prolonged periods. 2, at this time intercourse, the male genitalia may bring bacteria into the vagina, menstrual blood is a good medium for bacteria and other microorganisms, bacteria are very easy to breed, along the endometrium within many tiny wounds and ruptured small vessels spread, infecting the endometrium, and can even involve the fallopian tubes and pelvic organs, thus bringing unnecessary trouble to the woman 3, menstrual secretions into the male urethra, may also cause urethritis. Zhou Jing, Department of Obstetrics and Gynecology, Southern Hospital of Southern Medical University 4, coitus during menstruation, because the sperm in the endometrial break and the overflow of blood cells meet, and even into the blood, can induce the production of anti-sperm antibodies, thus leading to immune infertility and sterility. 5, coitus during menstruation, due to the contraction of the uterus during sexual impulse, may also squeeze the endometrial debris into the pelvis, causing endometriosis and leading to infertility. Therefore, for the sake of both bodies and the common future, never go for an exception, and if necessary, other methods can be used to solve the problem. However, regardless of the circumstances, the same party during menstruation should be prohibited.