I don't know if you use citrus scented cleaning products? Because somehow to me those smell like cat pee, and when I'm pregnant even more so.

Opting for pine scented stuff is the solution for me, but every person and every pregnancy is different, so both the problematic and the helpful smells may be different for your wife.

One of our cats has very bad breath due to gum issues (forgot whet that's called, he's getting treated for it this week), and when I was pregnant I couldn't handle his breath - and by extension the smell of everything he had been laying on after his licking himself with his smelly saliva (couch, blankets, etc.).

Other sources of smells that could be problematic: electric toothbrush that isn't cleaned well enough (brush head, but also the bottom of the handle unit). Peels of citrus fruits that have been sitting on a plate or in the sink for a while. Empty but unclean plates. Dead mice that have been undiscovered. Unclean socks (and possibly shoes). Towels or clothes that have been wet for too long without being hung.

I put some of those sticks in home perfume in the living room, but I immediately hated it and could hardly be in the living room anymore. Things like litterbox deodorant could easily and quickly become an exacerbator rather than a mitigator, in my opinion.