I have read it is not safe to handle any garden chemicals while pregnant and inhaling was one of the risks outlined - just can't remember where I read it though.
I know it doesn't help you - but I make sure DH does all the outdoor chemical stuff for the time being.
If you really must do it before DH comes back - perhaps invest in a really good breathing mask as well as gloves (ensure clothes fully cover all exposed skin). And at the very least do it on a non-windy day and ensure you spray into the direction of the wind (so it is away from you) and not into it.
Hope that helps a little.
All the best.