Possibilities. Bacterial vaginosis can cause a “fishy” smell. Other possibilities include std’s like gonorrhea, trichomoniasis & chlamydia or pelvic inflammatory disease. If there is a retained tampon or a lack of proper vaginal hygiene those are potential causes. Yeast is usually odorless but is still a possibility. If a woman has a fistula or cancer that can also lead to odor. See your doctor if uncertain.