Also called crib death, it is the sudden and unexpected death of an otherwise healthy baby whose breathing has ceased, typically during sleep. Could be from sleep apnea due to immature respiration pace systems. Autopsies of victims show brainstem serotonin system abnormalities, which could result in irregularities in respiratory regulation. To protect against SIDS, parents are urged to put their babies to rest on their backs to keep the airway open and unobstructed.