So how will Souped-Up Astra Guy respond to this?
Actually, I set out to snap a "baby on board" sticker - but I came across this first, and I think it may be even more nauseating.
Worse still, from our point of view, it's a disaster as a piece of persuasive writing. To understand why, we need - as ever - to consider the reader and, first, the intended result.
It's possible, I suppose, that some people put these stickers in their car windows for no other reason than to make the unhappily childless feel completely terrible. But, in most cases, we must assume the aim is to persuade other drivers to exercise special care in the vicinity of the vehicle carrying this precious cargo.
So who is being addressed? Logic suggests that it must be the more reckless and antisocial kind of driver; the (usually) young male in the souped up Astra GTi who, especially when lagered up, is more likely than anyone to careen into the side of the family MPV, with tragic consequenes.
And what are the chances that Souped-up and Slightly Pissed Astra Guy will respond to this message: "A baby? Bless! Time I mended my mended my ways, and started to drive considerably more carefully."
Not good, I'd suggest. "Tiny person on board"? You might as well drive around with a sticker saying, "Smug middle class driver. Feel free to cut me up at the lights."