Tessa and I work out 3 days a week with a group of 10 new mamas and their babies. We often incorporate the babies into the workout as weights or our target (like, when we are jumping up and then touching the ground, we'll tickle our babies instead!) Now that most of them are moving around much more, the babies spend most of the workout playing in their gym-inspired punching bag play area! I love these mornings. The babies interact so well (most of the time) and I know it has been so good for me, physically, mentally, and emotionally, to get out and to the gym! Gina, our leader, is a championship Muay Thai Kickboxer, so you KNOW these workouts are not easy!
Check out Gina's link. There's a picture of me doing a kettlebell workout when I was 7 months pregnant!