i'd drop down dead if my OH knew what bathroom cleaner was!!! never mind anything to do with the fumes.
it is a bit odd though that he felt the need to do that in the middle of the night... maybe he wanted it to be extra clean for you?? he got a lot of stuff on his mind hasn't he, you need to ask him about it.
PS he did actually clean the bathroom, with bathroom cleaner on friday evening, but that was only cos the midwife was coming on saturday morning! he was miffed when she stayed downstairs...ha ha ha .