When uterine bleeding occurs every 21 to 35 days and is not excessive, it is deemed as normal menstruation. The typical range for menstrual bleeding duration is between two and seven days. If the frequency or quantity of uterine bleeding differs from the aforementioned range, or if a woman experiences spotting in between her menstrual periods, then it is categorized as abnormal uterine bleeding. Various factors can lead to abnormal uterine bleeding, with structural abnormalities of the reproductive system and ovulation disorders being the two primary causes.