Just like every child is different so is every pregnancy. However, I'm a STRONG believer that while exercise may greatly increase your comfort during pregnancy and speed up recovery, it will have little impact on your labor and delivery.
My first pregnancy was very fit - did run/walk and BodyPump up till 36 weeks, gained 25 pounds. Typical 12 hr labor, 40 min pushing and while weightloss after was quick, I streched the pelvic ligaments which took over a year to recover from. Trauma to the pelvic floor was evident in holding as little as 5 pounds. High impact would cause quite a bit of pain and had a hard time walking for days afterword.
Second pregnancy, I was already 40 pounds overweight -good thing was I only gained 11 pounds. Almost as soon as I got pregnant the ligaments loosened up and I was in pain again so I ceased almost all forms of exercise. I was miserable. Sitting around all day with that extra weight in the abdomin was hard on my body - sore back, scatia, stiff hips, bla bla bla - you get the picture. However, labor and delivery was a breeze! In fact, it happened so fast it caught me by surprise and as we were getting our coats on to go to the hospital I had that overwhelming urge to push - our daughter was born in the bathroom
I took of my pants, squatted down, two pushes later I had her in my arms and I stood up. Recovery from that was a breeze! Lifting and walking were no problem after #2, unlike #1.
Hopefully if #3 comes along I'll have a pregnancy like #1 and a delivery like #2! One can hope anyway