I remember how Stella was pregnant with Amy, and we were ready to announce it to the public (we kept it to ourselves for the first few weeks).
I came into work and my co-worker Meike was there. She asked how Stella was and I replied, "Gut; sie ist guter Hoffnung." Which literally means, "she is of good hope", but Meike twigged at once and replied, "Oh, that's nice! When's it due?" ("Oh, schön! Wann ist es soweit?"). Heh—fixed euphemisms.
Incidentally, when I looked up "guter Hoffnung" on Leo just now, it was marked "veraltend" (obsolescent). And translated as "to be expecting; to be in the family way". The latter phrase made me think of my father, who would often make fun of that phrase by saying, "she's in everyone's way", so I don't think I could ever say it with a straight face because I would instantly have the association in my mind!
What euphemisms do you use for being pregnant? Or do you always come straight out and say "I'm/my wife/my friend is pregnant"?
(One I find cute is "to have a bun in the oven".)