I'm not 100% sure that I want kids to begin with, but I can speak from my brother's experience. He has a big dog who is not an "outside" dog (whatever that is). I swear, this dog was my brother's BABY. He carried all 50lbs of this dog around like a baby and would sing to him, coddle him, the works...
My brother and my sister-in-law had a baby boy at the end of June and I swear that the dog has NO IDEA what's going. Its truly sad.
If I had a human baby in the next few years and s/he was allergic to Stewie, I'm not sure what I would do, but I cannot imagine giving Stewie up. He OWNS me.
Pets are not disposable and should not be given up at the whim of an owner. Making the decision to get a pet is a BIG deal -- you can even plan for it -- its not like they just fall into your lap like human babies sometimes do. Accidents happen.
If my human baby developed a rash, I would do my best to keep him/her away from my furbaby. If breathing problems developed and it seemed nearly impossible to have both, I would give Stewie to someone close to me so I could still see him and would know that he is OK (but I would probably wish that I could give away the kid. Let's face it -- I don't like kids
).