Just a warning, DON'T get a puppy! Puppies are HARD and with a newborn baby, likely to make you insane. I would wait till the baby is older to get a puppy, or adopt an adult dog from a shelter. The adult dog will likely already be housebroken, be past the chewing and nipping stages and you will know right away or just by asking the shelter staff if it would be a good dog around kids.
Puppies need to be potty trained. It took one of my dogs over a YEAR to stop peeing in the house.. the other took several months. They don't even gain complete control of their bladder until about 6 months of age. Small breed dogs tend to be harder to house train than larger breeds as they have smaller bladders and need to go out more often. My first puppy (25lbs as an adult) I had to take outside every 15 minutes when she was a baby, or keep her crated so she couldn't have an accident. The more accidents they have in the house the harder it is to get them to stop. Smacking them doesn't do any good as they don't know WHY they are being punished and just learn to avoid you instead. This can lead to aggression and biting issues as well. Positive reinforcement (praise and treats for peeing in the correct place) is much, much easier and helps build a good relationship between you and your dog rather than hurt it.
Puppies also need to be taught not to chew on things. This is especially difficult from about 5 to 7 months of age while they are teething. They will chew on your furniture, your shoes, your socks, your babies toys, cords, WALLS (looking at you Zoey!) just about anything. Large breed puppies tend to do more damage than small breeds.. they have more powerful jaws and can reach things smaller dogs can't.
Puppies also need to be socialized and taught basic manners. An un-socialized dog is an accident waiting to happen. If they have never met someone different from you and your family (different age, race, style of dress) they will be very frightened when they do encounter someone different and may be scared enough to bite. Puppies need to be taught ASAP not to jump up on people with their feet, ESPECIALLY large breed dogs as this can HURT and be dangerous to small kids, elderly people and preggo ladies (struggling with this one with the dogs at work right now!). They need to be taught not to bark at everything. They need to be taught not to steal food, not to raid the garbage can, not to steal socks out of the closet or toys from the baby room. They need to be taught not to resource guard food and toys from people (such as your child who may not know any better).
My advice for those with small children and likely lacking the time it will take to properly raise a puppy: Get an adult dog. 4 years + is going to be a really nice age. Shop local shelters and humane societies for the perfect match. You'll want a dog that's calm, well mannered, house broken and good with kids. Breed and size won't matter so much after that.. though I would suggest older labs. They tend to have very good dispositions after age four or so. Before that they are CRAZY.
Ok.. long post over. :-/