You need to call the dr and let them know. Good luck.
Placenta previa can result in miscarriage, yes, however it does bring along quite a bit of vaginal bleeding. My cousin is pregnant with one child and has placenta previa and spots often, at 20 weeks. I'm sure the extra weight of twins with placenta previa isn't helping, so the best you can do is stay on bed rest to make sure your babies make it! Good luck hun!