My cousin doesn't have kids, but if she lived near me I would have invited her to my baby showers.
Just because someone doesn't have kids doesn't mean everyone they know doesn't have kids.
That's true, but even if everyone you know does have kids, that doesn't mean you're invited to baby showers every week. Especially if you find the whole subject of children upsetting, as the author seems to, you also have the choice of mailing a baby gift, or simply declining an invitation, no further discussion.
I simply can't think of another situation where, "Do you have children?" is an obvious question to ask a stranger. Can you?