Having an unborn child is MUCH easier than taking a post-born. The post-born definitely have the adorable thing going on, but they are loud, stinky, messy, capricious and completely inconsiderate of those around them. I'd much rather do almost anything with an unborn than with a post-born.
Also, when you carry your unborn child, men you have never met will hold doors and carry things and knock themselves out to help you. Once you are dealing with a post-born, most of that stops. You need it more with a post-born, but you get it more with an unborn.
I never took an unborn to WDW...but I would.