We propose to go directly to the recommendations that will help achieve that goal.
Try to maintain a reasonable weight, meaning that the increase is the same only for the baby and placenta. Health monitoring will help in this regard.
Raise your legs about the heart and body at every opportunity you can, as you see in the picture, something is always better than nothing.
Avoid crossing your legs while sitting, if you can not help it for long. Try getting a massage on the legs, they are essential to a better rest and to relieve pressure on the lower limbs.
Raise the foot in your bed with pillows or a pillow placed under your mattress, the movement of "return" will be clearly provided. Still being summer, it is highly recommended that you use special stockings, or stockings called "anti varices.
Try to make circulatory exercises to improve, precisely, the general circulation.