baby position

I did my 20 weeks scan. And had a hard time scanning the baby due to the position ( baby was facing me) MIL says that during sleep I have to keep changing my position so that baby learns how to turn. The thing is I'm a heavy sleeper, so I will stay in one position throughout the night unless I wake up and I don't feel comfortable then I will change. Where else, my hubby is a light sleeper and he sleeps before me . When I toss and turn , he will wake up. So I reduce my movements whenever I'm in bed . Is it true that I have to keep changing my position when I sleep?