text: what is sudden infant death syndrome?   sudden infant death syndrome (sids) is any sudden and unexplained death of an apparently healthy infant aged one month to one year.  sids is a definition of exclusion and should only apply to an infant whose death is sudden and unexpected, and remains unexplained after the performance of an adequate postmortem investigation including (1) an autopsy, (2) investigation of the scene and circumstances of the death and (3) exploration of the medical history of the infant and family. generally, but not always, the infant is found dead after having been put to sleep and exhibits no signs of having suffered. some researchers want sids to be assigned only to infants of age between one month and one year because of the likely high rate of false positive diagnoses in the neonatal cases when congenital anomalies are difficult to find at autopsy and the rarity of cases after one year.  sids is responsible for roughly 50 deaths per 100,000 births in the us. it is responsible for far fewer deaths than congenital disorders and disorders related to short gestation; though it becomes the leading cause of death in otherwise healthy babies after one month of age.