Heavy or prolonged menstrual periods, or menorrhagia, are the most common type of abnormal bleeding from the uterus. Periods are considered heavy if there is enough blood to soak a pad or tampon every hour for several consecutive hours.
There are many possible causes of heavy menstrual bleeding. They include:
Hormonal imbalance, particularly in estrogen and progesterone; this is most common in adolescents who recently began their periods and women who are getting close to menopause. Hormonal imbalance may also occur if there is a problem in the function of the ovaries.
Fibroids or noncancerous tumors of the uterus; fibroids typically occur during childbearing years.
Adenomyosis, a condition in which the glands from the lining of the uterus become imbedded in the muscular wall of the uterus; this is most likely to occur in middle-aged women who have had several children.