It does say "the baby is riding", but it's not really "dirty" in any way... When said like that, without a context, 乗る usually signifies "going along" with some sort of flow... If you say "Let's play this game I found!" and someone is like "Hell yeah, WOO! GAME!!!", that person would be 乗っている.

Does it just mean "baby on board" (as in signs in the back window of a car)? Or can this be an idiom to mean "pregnant"? Kind of hard to say without seeing the shirt, although knowing Japanese t-shirts... may be not so much.

Last edited by Pangolin (2009 June 17, 12:39 pm)

I'm still a beginner at Japanese myself, but from the few hits on Google I've glanced at with that phrase, it seems that it sounds weird to Japanese ears,  or at least uncommon. It doesn't quite have the same idiomatic punch as the English version.

(They also seem to exclusively refer to the stickers used on cars, so the extension to pregnancy doesn't seem to exist either.)

One response I found slightly amusing:

「赤ちゃん乗ってるからオムツ臭いですよ～～」 って意味なんだろうな～～って思うようにしてます。