In the past 2.5 years with your GSD, how have you been socializing him? How has he been with all the other infants and children you've introduced him to in preparation for the addition of your baby?
How was he in dog classes? Can you contact your instructor and possibly set up some more sessions with them in a controlled environment?
I'm sure all the prep work you did, knowing a baby was coming into the house, will pay off. Of course we are all anxious but that's why we do all the work when we first get a puppy! To make them a real member of the family and train, socialize, introduce them before a situation arises.
The one thing we do that is bad (and hard to prevent with the uproar of a new infant) is completely change our normal routine and pattern, unintentionally IGNORING our dog and instead focusing all our lives around the new baby. So the normal 'dog time' and walks/training/house time are in an uproar so our dogs can be so upset and realize that it's CLEARLY the new baby's 'fault' because their humans aren't doing what they need to do with the dog.
NORMAL with a baby is what life should be. Not CHAOS with a new baby in the house and dog now an ignored problem and outsider. It's not your DOGS fault you had a baby, so to isolate the dog, treat them like they are 'bad' and as if they are being punished from something they never asked for or probably wanted isn't fair. Specially because it's so easy to do the work ahead of time for a smooth transition.
Introducing Your Dog to Your New Baby | ASPCA
Pets & Babies - How to Introduce a Baby to Your Pet - Parents.com
UCB Parents Advice about Pets: Introducing the Dog and the New baby
Introducing Your Dog to a New Baby | Animal Humane Society
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Glory B Wildhaus AX, AXJ, XF
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