The boxer is the only breed I would trust with an infant (of course you never want to completely trust any dog with an infant). Boxers seem to be very aware of their size in relation to small children. My boxer Katie has been the most gentle dog I have ever known. Be sure to train your boxer well (an extremely easy task) & you will never regret the decision to add a boxer to your family. I would recomend a female & be sure to include her in everything you do. She will thrive on it. Mine would forego food for affection any day of the week.
You need to be careful around any dog of any size with an infant. That doesn't mean you shouldn't get a dog, you need to be mindful. Never leave a baby / child unattended with a dog no matter how close they are. Check with a dog trainer (or two) to discuss when the appropriate time to introduce a dog to the family would be (my guess would be after the little one is born). I have two boxers who are just the best, but even so, I am watchful when they are around any kids. They rough house alot and you need to be in control of them so they don't knock over the kids. Training is a must!
I have seen boxers with all ages of children. They seem to have an awareness of their size in relation to the size of the child and seem to hold normal traits such as excitement and jumping up on people when they are around kids. They like to be in the action, whatever that may be, but I have seen boxers with babies who are only months old that, after introduced will just sit quitely with the baby. They are also great with kids when they can interact and play with them more as the kids get older.
We got a boxer pup when our son was 6 weeks old. So we had an 8 week old puppy and a 6 week old son. They are now both 1 and are the best of friends. My husband jokes that we are going to get another puppy when we have another baby! She lets him lay on her and pull at her. Wonderful!