1stTimer is right, DTDing while UTD is perfectly safe unless advised by a Dr not too and it can cause slight bleeding as i have read and been told by Dr's also

BUT I must say if at any time u feel discomfort i would advise to stop

when i was 12wks 5 days we DTD and the next morning i was bleeding now the night before when we DTD i felt uncomfortable but DP was enjoying so i kept going and yes ended up bleeding the next day, so PLEASE just stop if feeling any discomfort!