Just listen to your body. I was running up to 10km before my pregnancy but then really slowed down when I fell pg due to ms. I started up again around 16 but soon felt uncomfortable (it was hurting the muscles/ligaments (?) down below my belly), so reverted to just riding and swimming. I now exercise every day. I alternate between a 2.2km swim and a 10km cycle (sometimes if I feel like it, cycling over the gatway bridge).

If you have no pain and keep hydrated and don't feel sore or faint or push yourself too hard, there should be no reason why you can't keep going till you get a bit bigger.

Remember to stretch afterwards ... my cramps have increased so much more than my previous pregnancy, I am pretty sure this is due to the great deal of exercise I am doing. Stretching after exercise and before bed helps MOST of the time!

PS - I have no medical training - just pregnanacy training LOL!!