Abnormal uterine bleeding is any heavy or unusual bleeding from the uterus (through your vagina). It can occur at any time during your monthly cycle, including during your normal menstrual period.
Vaginal bleeding between periods is one symptom of abnormal uterine bleeding. Having extremely heavy bleeding during your period can also be considered abnormal uterine bleeding. Very heavy bleeding during a period and/or bleeding that lasts more than 7 days is called menorrhagia. For example, women may bleed enough to soak through 1 or more tampons or sanitary pads every hour.
A variety of things can cause abnormal uterine bleeding. Pregnancy is a common cause. Polyps or fibroids (small and large growths) in the uterus can also cause bleeding. Rarely, a thyroid problem, infection of the cervix, or cancer of the uterus can cause abnormal uterine bleeding.