Endometrial polyps, or polyps in the lining of the uterus, may cause a brownish discharge a few days before your period.
Endometrial polyp is a common uterine pathology of localized endometrial overgrowth of the uterus, which may be caused by high estrogen levels and inflammatory stimulation. Due to the irritation of polyps, patients may experience bleeding between menstrual periods, and brownish discharge when the blood mixes with vaginal secretions.
Generally single and smaller endometrial polyps are asymptomatic, but larger polyps can cause recurrent vaginal bleeding and can increase the risk of uterine infections, which can be clearly diagnosed by ultrasonography and polypectomy under hysteroscopy is recommended. For more information, please consult your doctor.