I am considering running a half marathon next October (I will be 4 months pregnant then). Not racing, just taking it slow (even walking if I need it!) and enjoying the day! The doc gave me all clear for exercising and I normally run 10k and more for a "standard run". I have done 4 half marathons in the past. I honestly think I am going to be fine - has anyone attempted longer distances when pregnant and did you have any problems?