Quoting für immer:" This is my first time being pregnant and am curious as to whether or not it is safe or even smart to ... [snip!] ... is good for both mum and baby whilst pregnant, though I figured I would ask some ladies who have already gone through this."
I am 18 weeks pregnant with baby number 2 and I do prenatal yoga in the morning and prenatal workouts in the evening, exercise is good for you and baby during pregnancy and as long as you aren't over doing it and you are drinking a lot of water. I'm not a doctor but I would say as long as you don't have any issues at least yoga/long walks should be fine. I'm still doing cardio and btw there is nothing wrong with doing ab work outs when you are pregnant. You need the muscles in your stomach to do their job more than ever right now, I don't do crunches but I do planks and modified crunches I also do bicycles and scissors, you can get on youtube and look up prenatal yoga/workouts.
ETA: I am 5'5 and I weigh 150ish, I lost 10lbs since I found out I was pregnant and have only gained a couple of them back. So I'm still not over pre pregnancy weight.