I have done lots of reading and catching up in this thread and always been interrupted! Now I find myself at the end of the thread with a million things to say about all the little paths that have veered a bit off topic, but I think I'll just answer the original question. I must say I've found it very interesting reading and I've probably refined my thoughts about the phrase as I've read along.

To begin with I wasn't sure how I felt- the way I've taken this phrase when used before has been that you don't have to martyr yourself to make your child happy- my decision to return to part time work may kind of fit in with this. To me (and I know that everyone is different on this) I couldn't possibly enjoy the thought of just being at home as all there was to me. I was getting to the end of the day being ratty and wanting to hand DD over to daddy for a break- I'm sure at this time DD was not stimulated or having much fun. Having my 3 days work a week means that I appreciate her when I am home and we're both enjoying it more. It wasn't about whose needs came as a priority as I was lucky enough to have a DH who could move to 4 days a week work and a mum and MIL who were happy to do the other days. So I think we went from an unhappy mum and baby to a happy mum and baby.

On the other hand, I have always found it a bit of a trite thing to say, as we know it's not always true - of course you can make yourself happy and not be meeting the needs of your baby, so happy mum = happy baby is not always true, as many previous posts have covered.

So here we go - my theory:
Happy mums and happy bubs are not always mutually exclusive - ie. the phrase happy mum=happy bub can be true.

But the reverse is also true sometimes- unhappy mum can = happy bub (when you're up for what seems the hundredth time at night!)- this unhappiness may be fleeting but you have to admit it's not exactly making you happy in the short term.

At the same time happy mum sometimes = unhappy bubs. This can be true sometimes in a negative light (ie parents neglecting children), but also in my mind can be something mums and bubs just have to cope with from time to time- eg if you are giving yourself that bit of pamper time, but bubs is more keen on making you feel guilty for it by screaming the house down when passed to dad to be looked after. Once again this unhappiness may only be temporary.

And of course unhappy mum can=unhappy bubs. None of us want to be here..

So I think I've covered all bases.

And for those of you who want to be intellectually stimulated I would love to draw a venn diagram for you!! (Just being cheeky!)

After all of that, to me happy mum = happy bub is not a useful phrase. Not only is it untrue, as previously discussed it's a throwaway line that would really be better off replaced with more of a statement of guidance, that still supports a mum who is making a decision that might result in any one of the above variables. And I think that both the mum and the bub's wellbeing have to be taken into account. Otherwise the advice comes off as sounding self righteous and encourages people to be martyrs for their children, when sometimes kids have to get a bit used to not getting it all their own way.

Well who knows if I've managed to convey anything at all useful here!! But such an interesting topic, thought I had to work through it a bit.