Sudden infant death syndrome Sudden infant death syndrome  ( SIDS ), also known as  cot death  or  crib death , is the sudden unexplained  death  of a child of less than one year of age. Diagnosis requires that the death remain unexplained even after a thorough  autopsy  and detailed death scene investigation. SIDS usually occurs during  sleep . Typically death occurs between the hours of 00:00 and 09:00. There is usually no noise or evidence of struggle.SIDS remains the leading cause of infant mortality in Western countries, contributing to half of all post-neonatal deaths. Sudden infant death syndrome Other names Cot death, crib death Safe to Sleep  logo Specialty Pediatrics Symptoms Death  of a child less than one year of age [1] Usual onset Sudden Causes Unknown Risk factors Sleeping on the stomach or side, overheating, exposure to  tobacco smoke ,  bed sharing Diagnostic method No cause found after an investigation and  autopsy Differential diagnosis Infections ,  genetic disorder