No, I don't think you can harm bub by pushing to do poos, but you could harm yourself. And you soooooo don't want haemorroids! I had the opposite problem while pregnant, but after the birth I had a hard time (no pun intended ). Pears, and pear juice, is fantastic for that (although, don't wander too far from a toilet!). And possibley a good look at your diet might help too if you always have this problem? Make sure you drink enough water too.