Menstrual bleeding may be abnormal in duration of flow, timing of the cycle, or quantity of blood loss. If a woman bleeds more than 80 ml per month, she will probably be anemic. The number of pads or tampons used with each period is not an accurate measure of amount of blood lost. For practical purposes we usually initiate an evaluation for menorrhagia in response to a patient's subjective perception of heavy menses.

Abnormal vaginal bleeding has many causes. An evaluation for menorrhagia should begin with visual inspection of the vagina and cervix and bimanual palpation of the uterus and adnexa. Serum thyroid-stimulating hormone measurement, complete blood count, and a pregnancy test should be performed.

Do all women with abnormal vaginal bleeding need an endometrial biopsy?
In women with abnormal bleeding a biopsy is done to make certain the patient does not have cancer or a precursor to cancer. The teenager with irregular, heavy periods probably does not need an endometrial biopsy. Since the incidence of uterine cancer rises after age 40 years, most physicians would investigate abnormal bleeding in women aged 35 years and older with an endometrial aspirate. Whether an endometrial aspirate is indicated in women aged 20 to 35 with abnormal bleeding is a matter of judgment. Less than 5% of endometrial cancer is diagnosed in women younger than age 40 years. If medical therapy for 2 or 3 months fails to normalize menses in a younger patient, endometrial biopsy should be considered.

In addition to age, other factors increase the likelihood that a women with abnormal vaginal bleeding might have endometrial cancer. Obese women, women with irregular menses, diabetics, and nulliparous women are at increased risk for uterine cancer. Unopposed estrogen use in the postmenopausal woman greatly increases her risk of uterine cancer. Early menarche and late menopause are also risk factors for endometrial cancer. Women taking tamoxifen are at increased risk for endometrial cancer. Tamoxifen is used as adjuvant therapy for estrogen–receptor positive breast cancer. It has an anti-estrogen effect on the breast but an estrogen effect on the female genital tract. Tamoxifen appears to promote endometrial hyperplasia, polyps, and carcinoma. This risk is more pronounced in women treated for more than 2 years Barakat.

Any postmenopausal woman with a uterus who is not taking estrogens and who has vaginal bleeding should have an endometrial biopsy. (Menopause is characterized by no uterine bleeding for 6 to 12 months.) Postmenopausal women on cyclic estrogen-progesterone should have an endometrial biopsy if bleeding occurs on or before the tenth day of progesterone (i.e., before withdrawal bleeding would be expected)(Padwick). Postmenopausal women on continuous estrogen-progesterone often have vaginal bleeding during the initial 6 to 12 months of therapy. Bleeding heavier or lasting longer than a normal menses should be investigated. Likewise, bleeding after the initial 6 to 12 months warrants an endometrial biopsy.