Aunt refers to menstruation, and blood in the first three days of menstruation is considered abnormal bleeding, which may be related to uterine fibroids, endometrial polyps, vaginitis and other factors. 1. Uterine fibroids: uterine fibroids are benign tumors formed by the proliferation of uterine smooth muscle tissue, uterine fibroids can lead to congestion and dilatation of the venous plexus of the endometrium, which affects menstruation, and some fibroids are also necrotic and infected, which can lead to irregular vaginal bleeding. 2. Endometrial polyps: high estrogen level or some gynecological inflammation will lead to endometrial thickening, long-term stimulation will make the endometrium overgrowth, the formation of polyps, due to the fragile texture of the polyp, capillary rupture will cause bleeding. 3. Vaginitis: vaginitis is a variety of pathogen infection, caused by vaginal inflammation, there will be increased secretions, vaginal itching and other manifestations, vaginitis is more serious, the capillaries in the vagina are congested, and if there is an erosion, etc., it will also cause a small amount of bleeding. The blood in the first three days of menstruation may also be caused by other factors, you should go to the hospital in time for a detailed examination, and follow the doctor’s instructions for the cause of the symptomatic treatment.