Sleeping with a baby in the bed can be extremely dangerous. Even adults who sleep in the same bed can accidentally injure one another as they sleep; a baby is far more vulnerable to any accidental hits s/he may receive. Babies have also been suffocating due to the more plush, and thus unsafe, bedding on their parents' beds. Research has also revealed that men (fathers) can be likely to roll over onto them. This practice is quite unsafe for a baby.
Parents should put their sleeping baby in a crib because of the chance of injury to the infant. It is always possible that a child fall out of bed or that one of the parents accidentally roll over and either smother or crush the infant. Co-sleeping is a bad idea.