During pregnancy, the most I walked was to work & back. I wanted to throw up during my whole first trimester so I didn't do an ounce of exercise. Once you've gone that long, it's hard to get back into a routine...especially with another little person along for the ride. Post-baby, when my son was about 2 months old, I joined Stoller Strides, a stroller fitness class for moms. It was WONDERFUL! I got back into a great routine and saw real results. It wasn't just a Sunday stroll, it was a real workout class taught by real trainers. I encourage all moms to go to www.strollerstrides.com and find one in your area. My location has recently disbanded, but it's good because I have a newfound use for our long-standing YMCA membership!
Next time around I'm going to be much more proactive during pregnancy (assuming I can stomach it). This article by Lisa Druxman, founder of Stroller Strides, gives you some great tips on how to prepare for pregnancy and get back in shape post-partum.