Dogs sense things until we do. Since I became pregnant my pit bull doesn't climb in my lap when I'm sitting down. Used to if I sat she was in my lap. Now she will just put her head in my lap or front feet and put her head on my belly. When my daughter was born (1st pregnancy) my mom's yorkiepoo made claims to her and has been "protecting her". She is now 5 yrs old and he still protects her from everyone lol. Dogs are interesting. Don't over worry about the dog. Just watch it's actions around the child. Most dogs love kids. Wish I could invite you to my group on Facebook where you can see how my child and pit are together lol. I share a ton of photos of them there.
Our dog went weirdly protective when baby was born, growled at anyone coming near the baby and slept right at the door every night (we kept stepping on her by accident).
I would keep an eye out for how he reacts... Also may be an idea to have him sleep outside the room for a month or so beforehand, so that when baby arrives he's not jealous if you need to kick him out. I think he'd be fine, dogs seem to have great instincts about that sort of stuff but you never know...