Dogs often see babies as being in the pack. So there way of teaching members of the pack (especially if they view that pack member as being weaker than they are) is by growling & nipping/biting. To get this to stop you must assert your dominance over the dog & teach the dog that he is not in charge... that the humans are in charge (you, your husband, & your children). So whenever your dog does something that is dominant in nature (growling for example) you must assert your dominance by making the dog lay down & roll over on to his/her back. This is what alpha dogs do in a pack. If your dog will not lay down by command, then you physically make him/her lay down (not by hurting the dog though, just firmly) & then if they don't roll over on their own (they will do this when they recognize that you are the boss) then you must roll them over yourself until they get the point. Sometimes you have to hold them there or repeatedly roll them over until they get it. When I do this with our dogs, I usually make them stay in that position for a short bit (30 seconds to a minute or 2 depending on what they did). You can help the dog to see your child as dominant by holding your child in your arm when you are doing this... the dog sees the child as an extension of you. You must gain control of the dog or else something bad could happen (biting). And always be right there with your child when they are around the dog. For more helpful information, tune to The Dog Whisperer on the National Geographic Chanel or check out books by Cesar Milan (the Dog Whisperer). HTH
Just wanted to add that I am very sad to see that there are so many ppl who say to get rid of your dog. In our house, our dogs are also our children & we would NEVER dream of doing this. Yes, the safety of our human child is very important but we would do everything in our power to rehabilitate our dog before we ever got rid of him/her. Dog are all too often thrown away (look at all the dogs being put to sleep in the shelters!). When your child does something wrong (say biting another child) you don't throw them away.. you teach them. We must do the same with our dogs.
Also, in response to another post... females can and often times are the dominant ones in a dog pack. Our female is the dominant one over our male.