Remember that this is a time to let your body work on making your baby and that requires lots of energy. Fitness levels can be maintained with just three to four hours a week of cardio, strength training and stretching. The upper limits of safety have not been established. The leading researcher, Dr. Clapp, recommends that women exercising more than seven hours a week be closely monitored by their health care provider. Make sure you are gaining weight appropriately.

Since I don't know your weekly schedule, I cannot comment on its safety. I would imagine that you can continue teaching three to four low-impact classes each week.

Remember to tune-in to your body and adjust your exertion accordingly. In the third trimester, when the blood volume and respiration increase and your heart rate goes up with less exertion, you might consider switching classes with someone who teaches water aerobics. It is much more comfortable than low-impact and provides more benefits to the pregnant body than low-impact. If you would would like more information feel free to ask me more specific questions as they arise. Good luck.