Yoga can be very beneficial during pregnancy -- it calms both mind and body. So take prenatal classes. But don’t do any poses on your back after the first trimester -- they can reduce blood flow to the uterus -- and avoid inverted poses during the second and third trimesters. (Though some experts say that second trimester inverted poses may be safe if you’ve practiced yoga for a long time; ask your doctor.) Steer clear of Bikram or "hot" yoga; it’ll heat your body excessively.