Abnormal uterine bleeding can be caused by many different conditions.
Abnormal uterine bleeding in young girls.
Bleeding before the first period in a girl’s life is always abnormal. It may be caused by trauma, a foreign body such as toys, coins, or toilet tissue; irritation of the genital area due to bubble bath, soaps, lotions, or infection; urinary tract problems or sexual abuse.
Many girls have episodes of irregular bleeding during the first few months after their first menstrual period. This usually resolves without treatment. If irregular bleeding persists beyond this time, or if the bleeding is heavy, further evaluation is needed.
Abnormal bleeding in teens can also be caused by pregnancy, infection, & bleeding disorder or medical illnesses.
Premenopausal women. Erratic bleeding can occur in women who use hormonal birth control.
Hormonal birth control, like, pills, ring or patch, may experience breakthrough bleeding between periods. If it persists for more than a few months, evaluation may be needed &/or a different birth control pill may be recommended. Initially, women using injectable contraception or progestin-releasing intrauterine devices often experience irregular bleeding; over time, bleeding stops. Infections of the cervix, like chlamydia or trichomoniasis, can cause irregular bleeding, particularly after sexual intercourse.
Breakthrough bleeding can also happen if a hormonal birth control method is forgotten.
Some women do not ovulate regularly & may experience unpredictable vaginal bleeding.
The most common causes of bleeding are uterine fibroids, uterine adenomyosis, or endometrial polyps. Fibroids are benign masses in the muscle layer of the uterus (myometrium), while adenomyosis is a condition in which the lining of the uterus grows into the myometrium. Endometrial polyps are fleshy, usually benign, growths of tissue which project into the uterine cavity.
Other causes include: pregnancy, cancer or precancer of the cervix or the endometrium; infection or inflammation of the cervix or endometrium; clotting disorders such as use of anticoagulant medications, von Willebrand disease, platelet abnormalities, or problems with clotting factors; & medical illnesses such as hypothyroidism, liver disease, or chronic renal disease.
Women in the menopausal transition. Before menstrual periods end, a woman passes through menopausal transition or perimenopause, when women are more likely to experience abnormal uterine bleeding & they are also at risk for other conditions that cause abnormal bleeding, including cancer, infection, & systemic illnesses. Further testing is needed in women with persistent irregular menstrual cycles or an episode of profuse bleeding.
Women in the menopausal transition still ovulate sometimes & can become pregnant, which can cause abnormal bleeding.
Menopausal women. Women who take hormone therapy may experience cyclical bleeding. Any other bleeding that occurs during menopause is abnormal. Causes of abnormal bleeding during menopause include: Atrophy or excessive thinning of the tissue lining the vagina & uterus; cancer or precancerous changes of the endometrium; polyps or fibroids; infection of the uterus; & use of blood thinners or anticoagulants.
Source: UpToDate 2021