I did high impact aerobics until about 6 weeks before my first son was born (swam and walked up to the due date). Same thing for the second one. I was back exercising after 3 weeks both times and back to my pre-preg. weight after four months. But... listen to your body. I would be VERY careful about exercising in the heat in AZ (I had both my kids in Tempe, so i know about this). Raising your core temperature is not good for the baby. I have personal experience with this, won't go into details, but you might want to work out inside if it's hard to keep your temp. and HR lower, at least until it's cooler out.

Robyn