Sorry your dogs got into a scuffle and you got bit. When my girls were babies and toddlers, I had a food aggressive/toy possessive dog. I never had a problem with my kids and the dogs. I taught my kids that the dogs had times and places they were not to be bothered and food and toys were those times. I taught my dogs the same thing and that was to leave the kids alone. I let them smell, but never get too close when they were really little. My kids never played on the floor with their own toys unless I was right there with them and that should be a safety thing any parent with any dog should follow. As kids get older, they will mimic their parents and they will try to stop a scuffle if one breaks out and in my opinion that is when children become vulnerable. Teach them to get help rather than try to break it up. Training with both animals and children starts the minute the baby is born. Baby gates. Lots of baby gates.
Having said that, my youngest daughter has a more passive personality. She lets animals (large as in horses and small as in our dogs) walk all over her and doesn't take her own stand against them. I had to watch her especially close because animals sense that with humans the same as they do with other animals and they will learn to take advantage. You can never let your guard down. I always try to think of all possibilities then take precautions against them, and even still I find I have missed something.
On another side note, I have been around pregnant animals my whole life, cattle, horses, dogs, cats, you name it. You put one pregnant animal in a mixture of non pregnant animals and everything changes behavioral wise. Most times, the pregnant one was the instigator of negative behaviors.
Your Sadie may be feeding off your your horomones and senses things are not the same. She probably needs some extra attention and reassurance, and even more once the baby arrives.