You're pregnant, not dead or disabled. I lead a running group and I've 3 different ladies who've run up til their 8th month, and only stopped 'cause they couldn't find comfortable running shorts!
As long as you were fit enough for such a challenge BEFORE you got pregnant and have kept your fitness level up as best you can, by all means do it! I'd still get the ok from your doctor or mw that your not high-risk for anything, and listen to your body during the race (don't get overheated or, as tinytoes says, overworked - keep your pace comfortable), then its all good! Good for you! enjoy it!
