Crib death: The sudden and unexpected death of a baby with no known illness, typically affecting infants from 2 weeks to 6 months of age while sleeping. Crib death is now called Sudden Infant Death Syndrome (SIDS). Babies at an increased risk for SIDS include those with a brother or sister who died of SIDS; children whose mothers smoked or used heroin, methadone, or cocaine during pregnancy; infants born weighing less than 4.4 pounds (2000 grams); children with an abnormal breathing pattern with long periods without taking a breath (apnea); and babies who sleep on their stomachs. Since babies who sleep on their stomachs are at least 3 times more likely to die of SIDS than babies who sleep on their backs, children's health authorities such as the American Academy of Pediatrics recommend always placing infants on their backs to sleep.