I have twice ,but it depends on what kind of previa you have and how far along you are. So mine were found around 20 something weeks as you get bigger the previa can correct itself by moving up and out of the way of the cervix which mine did both times. However if you have a complete(I believe it's referred to) then typically they schedule you for a c section or if the previa doesn't correct itself after a couple of weeks they'll opt for a c section.