Depends. By 7 months, do you mean you are seven months pregnant? And if so, yes, we like our patients to lie on their left side as it takes the pressure off the vena cava your main vein bring blood back to your heart, if it is blocked, you cannot get as much blood to your heart to put out for your baby. If you are having left leg pain, you need to find out why. See your dr! Special beds let you lie prone.