Presently, guidelines from the American Academy of Pediatrics (AAP) say that bumpers are fine as long as the pads are not "pillow-like" and are securely attached to the crib. But the AAP may change its recommendation in the future, as the study found firm pads can be dangerous, too (trapping an infant's head in the space between bumper and mattress). So for now it's safest to avoid using bumpers --or at least practice these tips:
Go mesh. A breathable mesh bumper that's snugly attached should be a safer way to keep little arms and legs from slipping through the rails.
Keep ties short. The study found bumpers on the market with ties longer than 9 inches, which are a strangulation hazard. After you've tied on the bumpers, make sure you trim any excess.