My Patterdale was a rescue so I have no idea how old she was, probably about 7...we had her 3 weeks when I found out I was pregnant. I had Hg and she used to sit with me by the loo as I threw up for hours and just lick my hand... She was my shadow.
When dd was born she was amazing! She would lie on my lap under dd while I fed her because I have a buggered shoulder and would struggle to hold dd in one position for the length of her bottle feed. Dog would sit under the moses basket/cot if dd was asleep... She would come and lick my hand if dd murmured and I was asleep (and nip my finger tips if she thought I wasn't getting up fast enough!)
She had really tight curls on her ruff, dd would grab at them and pull, we would stop her and take her hand to show her how to stroke, dog never batted an eyelid.
We had heard of one's who hated babies for the noise etc, but with my dog she was amazing! She loves dd to bits and would have let her do pretty much anything to her!
I was gutted when she developed dementia and we had to put her down... She became very aggressive toward a our other dog... Like trying to rip his throat out. I couldn't risk her hurting a person so had her pts.
Every dog is different, you know yours. If she/he is good with your older kids and you teach baby from the word go to give it space and be gentle you will probably be fine.
But remember any dog can turn if frightened or threatened