I'd congratulate her, but that seems awkwardly like congratulating someone for taking an extremely large dump.
Yes, pregnancy makes you ungainly and uncomfortable, and it's painful at the end... but the hard part is what comes next. (Really, all she needed to do to get to this point was [1] have sex [2] avoid getting punched in the gut [3] eat right.)
So instead of congratulations: good luck, you'll need it.