Miss Manners defines blather as those things people say when they're looking for words, but not wanting to use conventional phrases, that usually are totally inappropriate. ( Hint: We have conventional phrases for a reason. They keep feet out of mouths.)
Prime example of blather: (to a woman you don't know, or don't know well) "Oh! When are you due?!" Your foot goes into your mouth when she replies, frostily, "I'm not." or "The baby was born last month." See how much trouble being creative can cause? Pro tip: If you're close enough to her to know about an immanent baby, she'll have already told you. Don't ask.
I have been experiencing a LOT of blather recently, so as a public service I am offering this list of Things That Should Never Be Said To a Pregnant Woman. If they confuse you, refer to the translation of What She Actually Heard. Or just take my word for it.
1) "Oh! You must be due any day now!" (What She Heard: "You're enormous!") Your foot goes in your mouth when she replies "No, actually, not for another two months." I started getting this comment at least two months before my actual due date. If you don't know when the baby is due, do everyone a favour and don't try to guess.
2) "Wow, are you having twins?" (What She Heard: "Really, you're ENORMOUS!") This is especially bad as a follow-up to the previous question, after you've discovered that she isn't due for weeks. A restaurant server said this to me just last week, after trying #1 first. Fortunately, one of us knows how to behave in public, or it could have gotten really ugly.
3) "You're huge!" There is no way to rectify this. You may as well just go about with a bag over your head from then on. You're simply doomed to social failure, unless it is obviously a cultural misunderstanding. Even then, you're on shaky ground. (Want to know why pregnant women don't like being told they're huge? They already know this, it isn't flattering, and they're tired of hearing about it.)
4) "You look really uncomfortable." You think you're being so empathetic, but What She Heard was "You look enormous, and miserable to boot."
To summarize: If what you're about to say gives any indication that you have noticed a woman's belly is a bit larger than normal, shut your mouth quickly. When you've recovered from your glance into The Pit of Doom, open your mouth again and state, in your most sincere voice "You look lovely today." (If there's no way that would be believable, just keep your mouth closed.) It's so much easier than trying to be original, and it will taste lots better than your feet would.