Sudden Infant Death Syndrome (SIDS) is the diagnosis given for the sudden death of an infant (baby under 1 year of age) in their sleep that remains unexplained after a complete investigation. The investigation includes an autopsy, examination of the death scene, review of [any] prior symptoms or illness, and review of pertinent family medical history. The death is usually caused by respiratory while asleep, and is also commonly known as "crib death". It is the leading cause of death in infants, and is most likely to occur when the baby is between 1 and 4 months of age. More boys die of SIDS than girls. African American and Native American babies are about three times as likely as caucasian babies are to die of SIDS.

Though there is no accepted cause of SIDS, there are many theories and apparent risk factors. The two most commonly known ones are putting the infant to sleep on it's stomach and if the mother smoked while pregnant. While asleep, a typical SIDS child will experience episodes of sleep apnea in which their heart rate slows down and breathing stops. A theory as to why the child does not wake up the way most children do when their brains sense insufficient oxygen is that there is an underlying brain abnormality or problem in the nerve cell development, such as a flawed arcuate nucleus. Infants of mothers who smoke are likely to develop these abnormalities because, as a fetus, it [did] not receive the amount of oxygen needed for proper development. The tissue of the respiratory system mat also develop abnormally. A mother who smokes is three times more likely to have a baby die of SIDS. Babies exposed to passive smoke are two time more likely to die of SIDS. Infants who sleep on their stomachs are more likely to rebreathe exhaled air that is trapped in the bedding; the decreased levels of oxygen may cause the respiratory failure.

Other risk factors include a previous or current respiratory infection, excess dioxide intake, overheating, too soft of bedding, metabolic disorders, and air travel while pregnant. Infection and excess dioxide intake at a young age may weaken the developing respiratory system and increase risk of respiratory cessation. Soft bedding has the same affect as sleeping on the stomach: air becomes trapped. Some babies who die suddenly may be born with a metabolic disorder. One such disorder is medium chain acylCoA dehydrogenase deficiency, which prevents the infant from properly processing fatty acids. A build-up of these acid metabolites could eventually lead to a rapid and fatal disruption in breathing and heart function.

There is no way to detect and cure the disease. However, the risk factors can be avoided. parents are encouraged to get proper prenatal care and see the doctor regularly once the baby is born. The proper care includes not smoking, drinking, using drugs, of exposing the fetus to any other form of toxin. Parents should also lay the baby down on their backs in a crib with a firm mattress unless told otherwise by their doctor. CPR may revive the infant if started soon after the breathing stopped. SIDS is devastating to the family and other caregivers involved (doctors, babysitters, EMTs), and they are recommended to seek counseling to help them deal with their loss.