It is very responsible of you to come here and ask.
Given what I know about babies and German Shepherd puppies, I would wait to get a German Shepherd puppy when my child or children are at least six or seven.
Human babies are overwhelming for first-time parents. German Shepherd puppies can be overwhelming for first-time owners. I can't imagine having both at the same time.
I'm sure a lot of people will come on here and say it can be done. Yes, anything can be done. What would be best, my opinion, to see how you do with the baby before adding a dog to the mix.
Best of luck with whatever you decide to do.