alien, it's your decision to make - in the first trimester the uterus is behind the pelvis, so I have been told. I will be playing my sport up to 12 weeks (there's a risk of being hit, or falling onto my front at pace) - though I am slowing down already so I may not be selected for my team at this rate! I played to 15 weeks last time but only in friendly games, and I felt it was a bit much as I struggled to stay bent over my stick - skiing might be the same, possibly.
The advice now seems to be no contact sports, no sports where you risk falling (skiing, riding, cycling), and no sports with a risk of contact (football, hockey etc) right from the start of pregnancy. I have chosen to ignore that advice for the early months. I know how to fall, and like you, I stand about the same random risk of falling down the stairs, being in a car crash, slipping on ice etc.
If I were you, I'd still go, but would stick to the easier runs and not take any major risks. Do be careful though as with the stretchier ligaments you could make life quite uncomfortable for yourself if you twist or sprain something - are you doing core exercises now to build up strength?