My one roommate in college was pregnant her senior year (our junior year), and she got sick *once* her entire pregnancy. She was also able to hide it until about her 36th week, and she delivered at 38 weeks! She barely showed at all. In fact, I drove her to the hospital the one day because she thought her water broke, I went back to the dorm, got ready for class, and by the time I was walking down the stairs, she was running up in the other direction. She gave birth that night. So the day she gave birth, she was running up stairs I, not pregnant at all, couldn't walk up wihtout getting winded.
