The interwebs are abuzz with discussion of this woman who completed the Chicago marathon despite being 39 weeks pregnant. Some laypeople say that she was stupid to do this and put her child at risk. Others, including various physicians, say "You go girl!"
The thing is, she had her physician's permission. She was in excellent health and was very much used to running. In addition, she didn't run the entire distance; rather, she walked for about half of the course, and she averaged out to about four miles per hour -- the equivalent of a brisk walk. She also listened to her body, watching to see if she was getting light-headed. Heck, she didn't even expect to finish the marathon, but she did.
I say "You go, girl!"