Starfish, I agree with Wysiwyg, they may simply be assuming you want less responsibility now. I know when I returned to work in October last year, I certainly didn't want to work at the same level that I had before maternity leave. My priorities had simply changed.

You could chat with someone about it or come at it from a lighthearted angle...

Jokingly say " come on folks my brain needs a good work out after all the goo goo ga ga talk I've been up to at home! Bring it on!"