What I did to introduce my baby to my doggie was to sent my dog to my mum's place (the idea is to get him out of the house, bringing him out for walks does work too) before I brought my newborn home. When the dog comes back home, I will then introduce my baby to the dog, leading him to where the baby is and explain to him. In this way, the dog will not feel that the baby is invading his territory.
When a child can distinguish this is the animal
I introduced my kid to our dog from birth
Some babies are allergic to doghie
Take care