I found a fantastically useful (and humorous) book called "Attack of the 50 Foot Hormones" by Emma Tom. She speaks briefly about inane comments she's heard and her responses. My favorite:
(To someone very heavily pregnant) "Are you still pregnant??"
"No, I stuffed my daughter up my sweater 'cos I enjoyed being pregnant so much".
I know people are nosy, curious etc. What bothers me is people not thinking before they speak. Of course this applies across the board, not just in the case of pregnancy. It doesn't hurt to pause for a sec and think "is my comment going to be in the least bit helpful in any way? No? Then I think I'll just zip it".