Not only is it discussed in nursing journals, but since 2008 the BMA has requested that nurses stop addressing patients and relatives in an informal manner, because so many people find it offensive and/or distressing.
Research at Yale (by Levy) has shown that HCPs who speak to elderly people in a patronising manner by calling them by first names and terms such as 'sweetie', 'love' and 'dear' can shorten the patients' lives by 7.5 years because it infantilises them and makes the patient view themselves as incompetent and unworthy of respect. This psychological effect reduces their chances of coping with getting older, and is particularly bad for people with any kind of mental health problem such as alzheimer's because the person is already struggling with keeping hold of their sense of identity.
I would think similar issues would apply to mothers of young children, as such women often do struggle with feeling like they are losing their identity, post-natal depression, feel they are less competent than child work professionals and so on.
For people to dismiss this issue as trivial may represent the views of some nurses, but it does not represent the views of doctors, and this has been made clear by the BMA request. The reason this issue matters is because people are in life and death situations, and this makes people feel very vulnerable. I have been through this with both myself, my DS and my DH when me/they have been in hospital. I don't want any of us reduced to some generic term; we are individual people and should be treated with respect during treatment, illness and emergency.
There may very well be some people who want to be called 'mum', 'love' or 'sweetie' by a complete stranger just because the stranger has a uniform on, but then some women want to be called 'darling' when they walk past a building site. Most of us don't want to be patronised, so please stop. The suggestion that I should allow a nurse to call me whatever she likes just because she did her job by not allowing my child to die in hospital - well it is a disgusting and offensive suggestion.