I'm not sure about "big" stores, I do know that C&A has some maternity wear available, the one here in GrosseBasel (near Barfüsserplatz) has the maternity stuff near the plus size stuff... they go all the way up to size 50.

So far as other maternity things, I'll offer that when I was looking for bras and such, the women who I asked in the various shops were quite helpful in directing me where else to look if they didn't have what I needed.

I couldn't find any larger size bras (let alone nursing ones) in my size (42DDD) in any of the local stores for prices I was willing to pay - 120+chf is NOT an amount I am willing to pay for a bra - or in fabrics I'd like - Nina had some pretty stuff but it was all lacy, not something that someone who is pregnant and (sorry guys!) experiencing sensitive skin issues would want to have to deal with.

Meanwhile, Bonprix catalog carries larger size bras, unfortunately not nursing ones that I saw, but they even have cotton and "t-shirt" (seamless cup) bras for 20 to 40chf.