Five days before menstruation, coital bleeding is generally caused by a variety of reasons, bright red and dark red blood of the specific causes are different, as follows: 1, bright red: if the color of the bleeding is bright red, often cervical bleeding, for example, sometimes a woman’s cervix has an erosion or polyps and inflammation, these are prone to lead to the bleeding of the coitus, the gynecological examination can be found in the hospital. 2, dark red: if the color of the bleeding is dark red, often cervical bleeding, such as some women have endometrial polyps, endometrial inflammation and endocrine disorders can lead to the bleeding. 3, dark red: If the color of the bleeding is dark red, we should consider the cause of the uterine cavity, for example, some women have endometrial polyps, uterus is endometrial fibroids, endometrial inflammation and endocrine disorders can appear uterine bleeding, this situation should go to the hospital to do ultrasound and gynecological examination to identify the diagnosis.