When our son was born (19wks) we made sure our Jack Russell wasn't left alone with him, and just allowed him to see and sniff the baby so he got used to him. He's a very boisterous dog, but not nasty at all. We did worry he'd be jealous, but i think we've got their relationship about right.
BUT it's worked too well- when my MIL had my son last week, the dog was fine with her, but growled and wouldn't let her near the baby. Any ideas? I don't want the dog to attack some innocent person.