You should ensure that the space between the mattress and the sides of the crib is less than the width of two fingers. You'll want to make sure that there aren't any curtains or drapery near the crib so baby can't grab on and suffocate. You should never put pillows, big floppy toys or plastic sheeting in the crib. Stay away from crib bumpers, because they actually put baby at more risk than you might think. Baby can roll and get stuck with his or her face against the bumper, leading to suffocation. While there are breathable bumpers, you should avoid them altogether. 

Pediatricians and medical professionals continually remind you that baby should be placed on his or her back to sleep, never belly down. When your little one is on his or her belly, they aren't strong enough to move their heads should they get stuck face down in the mattress. Until he or she can lift their head on their own and roll over without