What is SIDS?

A mother and baby room sharing. Baby is sleeping on their back in their own sleep space, in the same room as the parents, next to the adult bed. The mother reaches toward the baby, who is close enough to comfort but not in the bed.

Sudden Infant Death Syndrome (SIDS) is the term used to describe the sudden death of a baby younger than 1 year of age that doesn’t have a known cause, even after a full investigation.

Healthcare providers, law enforcement, and others investigate infant deaths to figure out what caused them. This investigation includes a complete autopsy, examining the death scene, and reviewing the clinical history. If they cannot determine a cause of death for the baby or explain why the baby died, the medical examiner or coroner may categorize the death as SIDS.

What causes SIDS?

Researchers do not know exactly what causes SIDS. However, they do have an informed idea, or theory, that may explain how SIDS happens. It’s called the Triple-Risk Model.

If a baby dies suddenly or unexpectedly during sleep, is it always SIDS?

No. SIDS is not the cause of every sudden or unexpected death of a baby during sleep.

The death of a baby that is sudden and unexpected and that doesn’t have an obvious cause before an investigation is called a Sudden Unexpected Infant Death (SUID). SUID is an umbrella category that includes all sudden, unexpected infant deaths—those from known causes, such as an injury or accident, and those from unknown causes, such as SIDS. SIDS is one type of SUID that occurs during sleep.

A baby can die during sleep from causes other than SIDS. Sleep itself does not cause SIDS or other sleep-related deaths.

How common is SIDS?

About 3,000 SUIDs occur in the United States every year. Of those, more than 1 in 3 are from SIDS.1 Learn more about SIDS and other sleep-related infant deaths data and statistics.

  1. Centers for Disease Control and Prevention. (2019). Sudden unexpected infant death and sudden infant death syndrome: Data and statistics. Retrieved July 1, 2019, from https://www.cdc.gov/sids/data.htm.