Background to rant: I've been back at work now for a month, after 7 months maternity leave. Since returning I have been demoted, so my boss (Director) is now the manager of my department that I built up from scratch, over 4 years. Alas I still get the same salary and my head of department signature is still on my emails. The reason for this is that I now work a 4 day week, so the thinking is I can't manage a department, although I am available every day. This situation is annoying me somewhat, and I feel devalued. But I can live with it for the first year of my babies life.
What is really getting my goat, is that I keep getting comments like the below, from someone I recruited:
"You are a mum now don't bust a gut"
"It must be hard for you to get organised at work, now you have a baby to organise too"
"Your priorities have changed, you focus on being a mummy and don't worry about creating new strategies"
I don't know how to handle it, or respond, without swearing, or coming out with a comment, like "you are a pain in the ...now"
Looking for some advice, or a few lines that I can say to combat, what I see as negativity, as it winds me up.
When I am at work, I am at work, I take off my mummy hat and focus on job at hand. It hasn't made me a poor performer, in the contrary, it has made me aware that I can achieve a hell of a lot.
What do you think?? How would you respond to a co-worker devaluing you as "you are a mummy now" ?
Thanks in advance for your support 
SarahG41