Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Well, yes, it may be caused by Postrino, but also occasional spotting between periods might have this appearance and can be normal, especially if you re taking low-dose birth control pills. So in most cases this is not sign of disease. If it is, then usually this indicates bacterial vaginosis, STD or polycistic ovarian syndrome. Less common, some other hormonal disorders may be present. In some cases, however, a yellow or brown vaginal discharge could indicate a serious problem. Although brown and yellow vaginal discharge often does not indicate a serious problem, it should not be ignored if it persists, recurs or is accompanied by other symptoms. You should see a gynecologist for further work up. In some cases, a yellow or brown vaginal discharge could indicate a serious problem. Wishing you good health. Regards