So sorry to hear your terrible news.

I have never shared my life with a dog with three legs, but my friend had a whippet with three legs.
She had a long and happy life, when she ran you couldn't even tell.
I know theres a big difference in a whippet and a gsd, and she was a very young dog when she lost her leg (r t a)
But I am sure your baby will cope.
Thinking of you and your baby, hope your dog heals really quick.
Mazz xx