Things not to say to a lady you suspect may be pregnant:
"Excuse me, but are you expecting? Oh, I didn't know, I just thought you looked chubbier"
Chubbier!!!???? Imagine if I wasn't! The shame!! People, if you ain't sure just don't say anything, it's much safer that way.
(And don't tell the lady's husband that she looks "stout". Stout isn't much better)