How do I know this? Hahaha! Surely you jest.
For some reason, anything related to childbirth tends to short-circuit common courtesy and tact. So, as a public service, I present to you a guideline for asking questions. There is just one simple trick:
Would a similar question (or statement) be appropriate when a woman is not pregnant?
For example:
To Pregnant Woman: "Do you plan to deliver vaginally or by c-section?"
To NotPregnant Woman: "What are your upcoming plans for your vagina?"
See? It's easy.
Still unsure?
To PW: "Was this pregnancy a surprise?"
To NPW: "Did you intend to have sex with your husband last Tuesday?"
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To PW: "Are you going to breastfeed?"
To NPW: "What do you intend to do with your breasts for the next year?"
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To PW: "Did you do fertility treatments?"
To NPW: "Are your breasts real?"
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To PW: "You look huge!"
To NPW: "My, you're fat!"
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To PW: "Should you be eating that?"
To NPW: "Should you be eating that?"
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To PW: *Pats belly*
To NPW: *Pats belly*
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To PW: "Are you pregnant?"
To NPW: "Are you pregnant?"
I don't care if the woman is "obviously" pregnant. Believe me, as someone who has been mistaken for being "obviously" pregnant, nothing is more demoralizing than a person checking out the box of Godiva chocolates that settled just south of your belly button and asking, "When are you due?"
As a rule, I would say that most women like to be (very) well-acquainted with someone before discussing their private parts, their sex life, their weight, or any of their plans for the future. (Of course, knowing what the college bar scene is like these days, maybe that's just me...) But think, people. Think before you speak. Realize that 99% of what is going on with any woman's body is absolutely none of your business, pregnant or not.
And if you simply must ask a question, try one of these:
"Would you like my chair?"
"You look beautiful!"
"May I help you with that?"
Or my favorite:
"Have some chocolate."
And please, please keep your hands to yourself.