What Is SIDS? - Definition, Risk Factors & Causes

Instructor: Jayne Yenko

Jayne has taught health/nutrition and education at the college level and has a master's degree in education.

In the United States, there are about 2,000 sudden infant deaths each year. Researchers have not figured out why it occurs; nevertheless, some strides have been taken to reduce the risk. Read on to learn more about this condition, the risk factors involved and what you can do to reduce the risk of SIDS.


SIDS or sudden infant death syndrome is the sudden unexplained death of an infant under 1 year of age. The baby is found dead after having been put to sleep and shows no sign of struggle. SIDS is the leading cause of death among infants between 1 month and 1 year of age, with the most cases occurring between 2-4 months of age. This phenomenon, also known as 'crib death', was first described in the late 1960s.

Risk Factors

All infants are at risk, but there are factors that may increase that risk. These include:

  • Gender - boys are more at risk than girls
  • Age - babies are most at risk during the first four months of life
  • Ethnicity - African Americans, Native Americans, and Alaska Natives are more at risk
  • Having siblings or cousins who have died of SIDS
  • Breathing secondhand smoke
  • Being born premature
  • Having a low birth weight
  • Having a respiratory infection

There are also maternal factors that can increase the risk of SIDS. These include if the mother:

  • is younger than 20
  • smokes
  • uses drugs or alcohol
  • has little or no prenatal care


SIDS is a sudden and silent medical disorder. The cause is still unknown, but there appears to be an association between SIDS and abnormalities in the part of the baby's brain controlling breathing and arousal from sleep. Since doctors started recommending babies sleep on their backs or sides, the incidence of SIDS has dropped dramatically. Unfortunately, SIDS is still a major cause of death and is not entirely preventable.

What SIDS is Not

It's important to understand what SIDS is not: SIDS is not contagious, nor is it the result of child abuse or neglect. It's not caused by suffocation, vomiting or choking, nor is it caused by vaccines or shots. SIDS is not caused by the cribs themselves.

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