The sudden and unexplained death of an otherwise healthy and normal infant during sleep with no sign of disease. It is the most common cause of death among infants between the ages of 2 weeks and 1 year occuring once in every 300 - 350 births. Causes of cot death are unknown although many theories have been put forward. Among them are a lack of biotin in the diet, an abnormality of the endgenous-opioid system, suffocation in the crib, a defect in the respiratory mucosal defence, prolonged apnea, an unknown virus, an abnormality of the larynx or immunoglobulin. The condition seems to occur more frequently during the winter months among children between 10 - 14 weeks. Children born prematurely seem more susceptible as are males. Other predisposing factors include a higher incidence among children born of women less than 20 years of age and have had at least one previous child, those who begin prenatal care in the third trimester and among mothers who smoke are anemic or drug dependent. Cot death is neither contagious nor hereditary but there is increased risk of occurence within the same family. Also called sudden infant death syndrome (SIDS) or crib death.