When I was 4.5 months my favorite thing to do was tell people I was half way through my pregnancy, then watch them try to figure out how many months that was.
One day a woman asked me, "How much do you have to go?" And I said, "I'm four and half months." She said, "Is that four and a half in or four and a half left to go." I smiled and said, "Both."
Now I'm pretty much at 5 months, and all the fun-with-math is gone. Wah.