It's pop quiz time. Which is the correct response? Situation: A heavily pregnant woman waddles into work. You thought her due date was a week ago. You say... A. "Wow, haven't you had that baby yet?" B. "Look out, here comes the bowling ball!" or C. nothing, but get out of her way. I'll give you a hint, it's not A or B. A nice "good morning" would be fine, but no need to mention the baby at all. If she's still waddling around, she obviously hasn't had it yet, so no need to ask her if she has. And likening pregnant women to round objects, or waddling animals, is just downright rude.
Unless you're going to be in the delivery room with us, it's also rude to inquire of the status of our cervix, or sex life, or tell us how much your labor hurt or how much went wrong. First of all, we don't especially want to discuss our cervix, mucus plug, hemorrhoids, or vaginal discharge with casual acquaintances, co-workers, or extended family. Occasionally, pregnant women like to pretend that our bodies are private and maintain the delusion that the various fluids and developments within are NOT topics of casual discussion. To a close friend, it might not be embarrassing to discuss, but better err on the side of caution.
Secondly, complete strangers need not ask personal questions such as "were you trying, or was it an accident?" (Nope this baby is completely unasked for, just like your comments) or "you do know they make a pill to prevent that, right?" (Why no sir, in fact, where do babies come from?) or, if we're having twins, "are they natural?" (Nope they're... alien babies?)
Thirdly, pregnant women worry enough. We don't need to hear how you were in agony for 36 hours before they rushed you in for a c-section and didn't let you hold your baby afterward. All these imagined fears are already floating around in our heads. We go through life wondering if our baby is going to come out with Down Syndrome, or need to be in the NICU for months, or have a fatal condition. We already think about labor like a soldier thinks about being sent into a war zone... will we survive? Unless you would willingly tell a new recruit about how your uncle was blown to bits in Iraq, don't tell a pregnant woman the grisly details of your friend's childbirth.
Penalty: Usually a nice, snarky comment is warranted. A glare and snarl also does the trick.