Yes, with placenta previa, you would have to have a C-section to prevent excessive bleeding and possible death of mother and baby. If the placenta is covering the cervix in any way, then the baby cannot move out and there lies your problem. It is very commonly diagnosed at 20 and 28 weeks, however. Many placentas start out low and then gradually move upwards. I was diagnosed at 20 weeks and then checked again at 28 weeks. At 28 weeks, unfortunately, it had only moved about 1/2 cm. So, I was placed on pelvic rest (nothing into the vagina) so as to not aggrevate the placenta and cause bleeding. I had a placental abruption at 31 weeks which required an emergency c-section. So, placenta previa is nothing to mess around with. And, like a PP mentioned, its a time when we thank OB's for being talented surgeons so they can save the lives of mothers and babies!