Prolonged menstrual bleeding is bleeding that continues for more than 7 days, according to the Mayo Clinic. Also known as menorrhagia, prolonged menstrual bleeding can be caused by structural problems within the uterus, hormonal imbalances or problems outside the reproductive tract, such as the use of certain medications or inherited bleeding disorders.
Hormonal Causes
The most common cause of menorrhagia is hormonal imbalance, according to the Merck Manual. Hormonal imbalances that lead to menorrhagia occur most frequently in women older than age 45 and those younger than age 20. Bleeding related to hormonal imbalances is often called dysfunctional uterine bleeding, or DUB. DUB is an imbalance between two reproductive hormones: estrogen and progesterone. When estrogen levels are higher than normal, a thick uterine lining builds up, and the resulting menses may be very heavy and prolonged. If the ovaries are producing estrogen but no egg is being produced, or if ovulation isn't occurring, the uterine lining will thicken excessively, and prolonged menstrual bleeding can result.
Tumors on the adrenal gland or thyroid disease cause hormonal imbalances that may result in menorrhagia. Polycystic ovary disease syndrome, or PCOS, is also a cause of hormonal imbalance that leads to DUB.
Uterine Causes
Uterine abnormalities are common causes of menorrhagia. Fibroids, benign growths of the uterus, affect as many as one in five women, Medline Plus, a service of the National Library of Medicine states. This can cause prolonged menstrual bleeding. Polyps, small fleshy growths that grow from the uterine lining, are common causes of menorrhagia in women of childbearing age. Adenomyosis, growth of the cells of the lining of the uterus into the muscular wall of the uterus, can cause longer than normal bleeding during periods, especially in middle-aged women who have had many children, Mayo Clinic says. Endometriosis, the growth of uterine tissue outside the uterus, is also responsible for some cases of prolonged menstrual bleeding. Cancer of the uterus, cervix or ovaries can lead to menorrhagia as well.
Other Causes
Many other problems can cause prolonged menstrual bleeding. Intrauterine devices (IUDs) used for contraception often cause menorrhagia, the Mayo Clinic states, and may need to be removed if blood loss leads to anemia. Disorders that interfere with the blood's normal clotting ability, such as von Willibrand's disease which causes a lack of certain clotting factors in the blood, cause menorrhagia. Taking blood thinners to prevent clotting or excessive use of anti inflammatory medication such as aspirin can also lead to prolonged menstrual periods.
