Not always. But once you have low lying placenta, you have to be very cautious. Try not to walk a long distance, avoid sexual intercourses, drink a gallon of water per day and if possible have 2-3 hours bed rest in afternoons.
I was told I have Placenta previa when we were 20 weeks. As I didnt followed instructions, began to bleed in 24th week. After 1 week hospital stay bleeding stoped. Now I'm at home almost all day, going out once a week and walking less than half mile.
You can use pregnancy belly band, it will help you to reduce the pressure that baby puts on placenta. It's less painful to walk with belly band.
I asked my doctor in 27th week ,whether I will have c section because of PP, she told me it's early to talk about it. As your uterus grows, placenta can move above.