Low lying placenta

Hoping some of you guys can put my mind at rest! Currently 20+1 with my 2nd child and went along for my 20 week scan today the baby wasnt playing so need to go back in a few weeks but the sonographer did tell me my placenta was low lying but prior to this I went for an early gender scan at 16weeks and was told my placenta was posterior.. is this common for the placenta to move around like this? I suppose I am overly worried because my 1st baby was emergency cesarean (3 years ago) and i was so so hoping for a vbac this time 🤞🤞 does being more active have any effect on moving the placenta? Just looking for people who may have had a similar experience x