what causes abnormal uterine bleeding
Abnormal uterine bleeding has many causes. It is sometimes caused by changes in hormone levels. It can also be caused by problems such as growths in the uterus or clotting problems. In some cases the cause of the bleeding isn't known. You may have abnormal uterine bleeding if you have one or more of the following symptoms: 1  You get your period more often than every 21 days or farther apart than 35 days. 2  Your period lasts longer than 7 days (normally 4 to 6 days). 3  Your bleeding is heavier than normal.