Actually only take bedrest if placenta privia is confirmed 100% and your nearing the end of your pregnancy. I am around 22weeks pregnant now with my second baby. I have an anterior placenta and was also told at a 20week scan that my placenta is slightly low laying.
The midwife said that in around 80%-90%of pregnancies the placenta will move upwards itself naturally as the pregnancy is developing. She told me to take light exercise, go for walks, and have a good diet. I will be scanned again at 34weeks pregnant to see if it has moved up naturally so we can discuss from there regarding labour or c section.
Im hoping it moves itself. Fingers crossed as i really dont want a c section.
You dont mention how far along you are in pregnancy? If its early stages or late. Late...then yes, rest up and take it easy. If its early, dont refrain from walking and being outdoors. Moving your body is a good thing! Just be gentle that is all.