I once had a problem with the pregnancy when the sim spun into maternity clothes after the carpool showed up, but before she left for work, but it was different from yours: the sim was both supposed to be at work (she got a job performance penalty for not being there) and not allowed to be (the "go to work" button on her career panel didn't work and the "work" option on her job building was greyed out). That pregnancy also took several game hours to complete the "spin into maternity wear, pat belly, get pregnancy moodlet" sequence, and she was frozen during that time. I ended up going back to my previous save and calling for a day off work before the carpool showed up - that solved the work problem.
Is your sim's appearance changing as the pregnancy progresses? (e.g. is she doing the pregnant walk, and is her bump getting bigger?) If so it'll probably work out okay - on the other hand after spinning into maternity wear she should have stopped vomiting and started getting backaches. Just in case, do you still have the save from right after she got pregnant, or is that possibly when your most recent .backup is from? Normally you wouldn't be able to go back to an older save because of the DecaDynasty rules, but Metro generally allows reasonable rule-breaking in the name of fixing bugs, and "Pregnancy is all glitched up" sounds like the kind of bug that "go back to previous save" is a reasonable fix for.