Loopy I hate mornings like that...But just think how beautiful your house will be when it's done!
OH woman is a little bit deluded IMHO. It's all very well suggesting these things to people but there's no thought behind how it will work. I'd think you have a few options (all based on my team/where I work so not exhaustive of course!)
Reduce your hours on a temp basis to miss rush hour
Use annual leave (as you won't be there for the full year anyway due to mat leave)
Work from home to make up your hours
All of this would have to be agrees with your manager I expect, do you have any "business demands" that would stop you coming in/going home at different times, how would this impact on other in your team? Your manager will have to know all of this before they would agree I imagine.
You'd have to pay back all hours in my (public sector) organisation unless this is part of a recuperative return to work plan after long term sickness.
You could, I suppose, start early and finish late and have a lunch with some "rest time" built in. Could be done as part of your risk assessment. In my experience (from ds) I carried on as normal for as long as possible and only made changes when absolutely necessary as you never know if you are going to feel worse/better as the pregnancy progresses.
Hope that helps, must dash 