My baby did not poop for 3 days. What can I give him to make him poop?

It depends really. I wouldn't worry too much if my baby isn't fussing and is still a happy baby. Feel his stomach, is it hard? Grab some baby oil and massage his stomach in a clockwise motion and finish off with bicycle kicks. You can do this if your baby is too young to take prunes. My son is formula fed and sometimes can go a few days without pooping. Just don't forget to monitor his stool once he poops! If it's small, hard and ball-like, chances are that he is constipated.