Re: Slim mother with a new born baby
there are trainers who specialise in workouts for expectant moms. if you're really interested, maybe you should give that a shot. but as niksik said, be sure to clarify this with your doctor first.
generally though, i've heard that being active is really highly recommended throughout your pregnancy, as it makes childbirth and recovery easier and quicker, relative to doing nothing while pregnant. i haven't yet been in that position, so i can't speak for this personally, but i keep hearing this from my preggo friends.