What are the possible causes of brown vaginal discharge?

Brown vaginal discharge typically represents old blood that has oxidized, giving it a brownish hue. This can occur for several benign and clinically significant reasons. Common physiological causes include implantation bleeding in early pregnancy, perimenstrual spotting (just before or after menstruation), or ovulation-related spotting. Hormonal fluctuations—such as those associated with starting or stopping hormonal contraception, perimenopause, or polycystic ovary syndrome (PCOS)—can also lead to irregular endometrial shedding and subsequent brown discharge.

Pathological causes warrant careful evaluation and may include cervical ectropion (commonly mistaken for “cervical erosion”), cervical polyps, endometrial polyps, or chronic endometritis. Infections such as bacterial vaginosis, trichomoniasis, or chlamydial cervicitis may present with brown-tinged discharge, especially when accompanied by odor, pruritus, or dyspareunia. Less commonly, persistent or recurrent brown discharge—particularly in postmenopausal individuals or those with risk factors—may signal endometrial hyperplasia, endometrial atrophy, or, rarely, endometrial or cervical malignancy.

Clinical assessment should include a detailed history (timing relative to menstrual cycle, duration, associated symptoms, contraceptive use, parity, menopausal status) and targeted physical examination—including speculum and bimanual exam. Diagnostic workup may involve high-vaginal and endocervical swabs, Pap smear and HPV co-testing, transvaginal ultrasound (especially to assess endometrial thickness), and, when indicated, endometrial biopsy or hysteroscopy. Any brown discharge occurring after menopause, following intercourse (postcoital bleeding), or persisting beyond two cycles warrants prompt gynecologic evaluation.