If you have intercourse twice in a row during your menstrual period, it is likely to cause reproductive tract infections, which may lead to infertility in clinical practice. Because in the menstrual period is the endometrium shedding caused by the vaginal bleeding phenomenon, if it is at this time to have sex, the pathogenic bacteria are likely to follow the open cervical opening into the uterine cavity and cause endometrial inflammation, and then into the pelvis will cause pelvic inflammation. Because the tubes themselves lumen is particularly thin, once the inflammation is likely to cause the blockage of the fallopian tubes, in the clinic will lead to infertility, so do not have sex during the period. In addition, if you have intercourse during menstruation, it may lead to endometriosis and dysmenorrhea, and in the most serious cases, it may lead to infertility.