By now you are getting used to the idea of being pregnant and hopefully all the unpleasant side affects have settled down. If you have been exercising regularly keep it up, consistency is the key to reaping the benefits of exercising while pregnant.  By now the fetus is large enough to put pressure on your vena cava (vein bringing blood back to your heart) so you should limit time spent on your back to 30secs. This means that you can no longer do the traditional sit-ups you did in the first trimester or other work on your back, instead you need to change to an incline or side-lying position. Remember, don’t overheat, don’t get exhausted or overtired, don’t dehydrate, and don’t over-train.