If you’re going to use a rhetorical arguments, you have to have something that makes sense. I can’t even imagine a scenario like the one your postulate, so if you hope to win this debate with anyone, find something else (I’m just trying to be helpful).
If you think a baby (fetus of course is the term used to dehumanize) is simply a burden (much like a parasite) there’s nothing I can say that will dissuade you. If you think single teens who have babies are saints, I have to wonder what your definition of saint is (since you’re not using the church’s definition, I think we can both agree!)
Lastly, dogs. Well, I happen to be heavily involved in dogs (not german shepherds, altho we had one when I was growing up, and yes, she was a great family member). I have trained, I have raised, and I understand that dogs can even seem like people. But, I know the difference. BTW they are NOT totally selfless. They just see us as their boss and their nature is to please us because that’s what their instincts tell them to do. Dogs are dogs, no matter how much we love them. What you call a fetus is a person.