Complete placenta previa-anyone have any experience?

I was shown that my placenta is completely covering my cervix at my 18 week anatomy scan. Which means a c section if it doesn't move and risk of bleeding during pregnancy. I've heard there is a high chance of it moving up as I get bigger from some people and others who say complete usually doesn't. My midwife said I don't need to be on bed rest or not have sex at this point...I've also heard mixed things on that.