How did you find out the baby would not be welcome? Was it just
because baby's name wasn't on the invitation, or was it stated
explicitly?

If it was stated explicitly, then I personally probably wouldn't go.
The only way I can think of you doing it would be if you could find a
babysitter to go along with you and sit outside, or in the vestibule or
lobby and you could check on the baby?

If you have not had a conversation with the couple yet, and if they are
close to you, I would talk to them about it. I had a similar situation
last year, when Lorelei was about eight months old. Her name was not
on the invitation. I emailed my friend and asked it was okay to bring
her, that I would come without her if necessary but would have to leave
the reception early. Not only did she tell me to bring her along, but
she seated us, with a highchair, at the head table. :-)

Can't hurt to ask!

Leslie