Either side Oso can
Left side is the best. But it’s ok for both side as long as not on your back
The best sleep position during pregnancy is “SOS” (sleep on side). Even better is to sleep on your left side. Sleeping on your left side will increase the amount of blood and nutrients that reach the placenta and your baby. Keep your legs and knees bent, and put a pillow between your legs
I tried to sleep more to the left although I love my right. 3rd trim onwards was more right because I could sleep much better which was important to get the rest!
Keerthi R