I'd personally rather have "sorry what was your name again?" rather than Mum. For many reasons.
- I'm a foster carer. For a number of children, I'm not actually Mum at all. Tell them Mum's coming in a minute, or make references to me as Mum, and they will think someone completely different is coming through the door. Try explaining that one. Again. To the child who both loves and fears the woman they do know as Mum.
Maybe that's exceptional, but if it weren't the default for too many people, it would be far easier for staff to stop themselves from doing it.
Next reason. It depersonalises and de skills me. Maybe it's subtle. Maybe not. But sit in a formal meeting about your child. One with a note taker, one with legal standing. Go around the room "hello, I'm Dr. smith, LittleBlue's paediatrician.""Hello, I'm Mrs. Jones, physiotherapist" Mr Lee, Miss James, Mandy Brown (nurses don't get to be mr or Mrs or ms), round and round the room. And then "And for the records, this is Mum."
I introduce myself by name; the note taker references me as Mum. Throughout the written report, professionals are addressed by name. I am called Mum.
Don't call me Mum.
I don't for a second believe that no one cares; the staff I've met do care, very much. It's habit, that's all. But it's one they could make the effort to change.
As several PPs have pointed out/suggested, a board by the child's bed. With names on. They do it the other way round - my nurse for today is Helen, my admitting doctor is Mr. Jackson. It wouldn't take seconds to look up and read "my parents names are" and fill in the gaps.
I'm an older parent now; it's not beyond the realms of possibility that I could have birthed some of the nurses on the ward. Don't call me mum.