Even though you should never leave a dog and a baby together by themselves there are certain dogs that would never do any harm to a baby on purpose. I have two dogs, one of them I know would never do anyone anyone any harm while the other I wouldn't leave it alone with an adult he doesn't know let alone a baby.
Well I consider myself to be very lucky here. Our dog is really really good with our son, who is three years old, and I can already tell that they are going to grow up well together and be best friends. This is what we wanted, too, so I am glad to be able to report this. We still worry about them being alone, but the size difference is not really a thing anymore it is starting to be less of a concern, but it is still there.
I have a 4-year-old nephew and he just turned 4 actually. Our family dog, Joe, a golden retriever, is 7 so he's been around before my nephew. He sees Joe as his friend and all of his friends see Joe as a friend. They just play with him and sometimes they torture him :), but Joe just frown his ears and put his famous smile on. he is a real sweetheart. My nephew is used to animals and especially dogs and the dogs get that very quickly so he goes around our neighbourhood playing with everything that is 4-legged.
Very strange story, when me and the wife had our first child my little mutt dog, who before then was always not that territorial, became like the super guardian of the baby. He would sleep under the crib and gnarl at anyone entering the room other than me or my wife. We didn't let him play with the baby till she was almost walking but he has always been right by her side. Even when she would yank his ears he would never show the slightest irritation.
I don't like doing it. You never know what can happen and the baby might provoke the dog in some way. I also don't trust a lot of theories so I generally keep my dogs away from young children.
If trust isn't an issue and I'm confident enough that my dog won't do anything to harm little children, then I will be okay leaving it in their company. Still, it pays to be cautious. For safety's sake, I or some member of the family should be around to check how things go while the kids interact with the dogs. Also, it's advisable to have your dogs vaccinated before leaving them in anyone's company.
Dogs like other animals rely on instinct when reacting to tactile and perceptive stimuli in the environment. Kids are won't to know how not to provoke the dog for instance, not pulling their tail which is quite sensitive. They are also likely to poke their hands into the dog's mouth and do the same to their mouth and might pick an infection if the dog is suffering from an illness. I suppose the best dog to leave your baby with would be a puppy.
I would be extremely hesitant to leave a young child alone with a dog. I think it is important to remember that both dogs and babies can be unpredictable. Even the most lovable pooch can get nippy if scared or provoked. If your back is turned, the child could pull puppy's tail, or something like that, and you just never know how puppy is going to react.
Is it ever safe to leave a baby or toddler in a room alone with a dog? Personally I don't think so, no matter how well behaved your dog is and how good it has been with children before your dog is still a dog and anything could happen. What do you think?
From my experience with dogs, I have come to realize that dogs actually are very babysitters. They can be very comfortable being with children, as you know very well kids loves and enjoy to play, so do dogs as well.
My dog is willing to play all day long as long as anyone is ready to encourage him playing, jumping up and down, turning on the floor. I normally engage him when I'm free but I try my best not to over do it, in order not to make him a playing freak.
Always have a young child with supervision when with a dog. No matter how gentle the dog is, we still don't know what is going through its mind and the baby also doesn't know what it's doing, so they might just hurt each other. Supervised playtime is encouraged, though.