I had 2 female cats that did that after I had a new baby years ago. But the ONLY places they peed were on the spots on the couch where I sat to pump breast milk. We had gone through many other changes, including major moves, etc. with the cats, and they had never done anything like this before, and they were never cuddly cats that wanted my attention anyway, so I always figured there was some kind of hormonal component to the situation. And if I moved to another spot to pump breast milk, they started peeing there, even if they hadn't seen me pumping there. Something in the smell of the milk was triggering something primal in them, I had figured. Unfortunately, we eventually had to give the cats away, because it never got any better!
With your baby, have you recently either stopped nursing, changed formulas, or started solid foods? It's possible that the change in the smell of the baby's food/milk has changed and triggered that female cat instinct, whatever it is! Or is your cat in heat or been in heat recently or soon to start her cycle? That also could have triggered a hormonal response in the cat. Just think how we women change with our hormonal cycles...female cats are also affected. I hope your situation has a better outcome than mine did!
Best wishes,
C.