Sudden Infant Death Syndrome

Sudden infant death syndrome (SIDS, also known as crib death) is the unexpected death of an infant for which postmortem examination fails to find adequate cause. It has a long history and has been explained, at various times, as infanticide, overlaying (accidental suffocation in a family bed), and thymus death, or status lymphaticus. The reasons why infants died suddenly were often obscure. In 1855 Thomas Wakley, the founder and editor of the Lancet, wrote about "infants found dead in bed," and there has been a stream of publications on the subject ever since. During the nineteenth century, the frequency of infanticide was a matter of growing concern. In the mid-1860s over 80 percent of all coroners' reports of murder in England and Wales involved infants. Disraeli said that infanticide was "hardly less prevalent in England than on the banks of the Ganges." The subject excited considerable interest in British newspapers and medical journals from the 1860s onwards. Death from overlaying was also common, perhaps because of overcrowding and the prevalence of drunkenness.

The unexpected death of an infant without obvious cause was long thought to be due to an enlarged thymus. This was a misunderstanding, but it lasted until modern times. Normal infants have large thymus glands, but most infant deaths occurred after prolonged illness had depleted the thymus so that postmortem examinations revealed small thymuses. A child who died suddenly was likely to have a normal, large thymus, and this was taken to be the cause of death. A disease, status lymphaticus, was invented to legitimize it. During the early twentieth century this disease caused considerable interest and anxiety. It was later questioned and eventually shown to be nonexistent.

Yet infants continued to die unexpectedly. During the 1940s the concept of crib death (also called cot death) became prominent and gradually the label changed to sudden infant death syndrome. Most experts in the field agree that it has many possible causes. These include infection (often sudden pneumonia), hyperthermia (overheating due to too hot a room or too many bedcoverings), murder, and unintentional poisoning (perhaps from cigarette smoke or chemicals, possibly arsenic, phosphorus, and antimony in crib mattresses, perhaps from obscure fungi that grow in old mattresses). The possible involvement of mattresses has led to accusations of cover-ups by governments and manufacturers. Increasing publicity has promoted the adoption of baby monitors, which record a baby's breathing and sound an alarm if the infant ceases to breathe.

The current consensus of opinion is that crib death appears to be an abnormal response to everyday challenges and stresses that do not affect most babies. After (or coincidental with) new regulations about crib mattresses and public advice to put babies into their cribs on their backs rather than on their stomachs, the incidence of SIDS fell by two-thirds, but it is still the largest single killer of babies under one year and the subject is of considerable interest to both pediatricians and the public. The Foundation for the Study of Infant Deaths initiates research and also campaigns for greater compassion to be shown by health professionals to bereaved parents.

See also: Infant Mortality; Pediatrics.


Bergman, Abraham B., J. Bruce Beckwith, and C. George Ray, eds. 1970. Sudden Infant Death Syndrome: Proceedings. Seattle: University of Washington Press.

Byard, Roger, and Stephen D. Cohle. 1994. Sudden Death in Infancy, Childhood and Adolescence. New York: Cambridge University Press.

Golding, J. 1989. "The Epidemiology and Sociology of the Sudden Infant Death Syndrome." In Paediatric Forensic Medicine and Pathology, ed. J. K. Mason. London: Chapman and Hall Medical.