Sudden infant death syndrome (SIDS) is the leading cause of death among infants 1 month to 1 year old. If the frequency of SIDS isn’t alarming enough, instances of SIDS also are unpredictable, are unexplained and usually occur quietly during sleep.

While there still are many unanswered questions about SIDS and other classifications of sudden infant death, researchers are getting closer to finding the answers and have been able to narrow down some main factors.

This is what you need to know about SIDS and protecting the infants in your life from sleep-associated deaths.

What is Sudden Unexpected Infant Death?

Sudden unexpected infant death (SUID) is a term that the Centers for Disease Control and Prevention introduced to help encompass all types of sudden and unexplained infant deaths, including SIDS.

The CDC breaks down the three causes of SUID as being SIDS, accidental suffocation and strangulation in bed, and unknown causes.

Because so much is still unexplained about SIDS, it can be difficult for medical examiners to distinguish SIDS from other cases of sudden infant death, particularly suffocation. SUID is a term to help clarify those distinctions and describe most sudden deaths among infants without an immediately obvious cause.

The CDC reports that there are about 3,500 cases of SUID every year in the United States. In 2014, 44 percent of SUID cases were categorized as SIDS, 25 percent were categorized as accidental suffocation or strangulation in bed and 31 percent were categorized as unknown.


The cause of SIDS is the topic of some controversy in the medical community, as there is no single known cause. A leading theory associates SIDS with abnormalities in the infant’s brain that affect breathing and arousal from sleep. This also is part of the reason why it’s impossible to discern SIDS from suffocation during sleep.

SUID most often occurs during sleep, and SIDS is sometimes referred to as “crib death.” The CDC reports a significant decline in SUID cases from 1990 to 2014, which is attributed to the American Academy of Pediatrics’ release of safe sleep recommendations in 1992, the “Back to Sleep” campaign initiative in 1994 (advocating for all infants to be placed on their backs when sleeping) and the release of the Sudden Infant Death Reporting Form in 1996.

Because the instances of SUID dropped so significantly during this time — in 1990, there were 130.3 SUIDs deaths per 100,000 live births, whereas in 2014, there were 38.7 per 100,000 live births — the infant’s sleep environment often is considered to be a leading contributor to the problem.


Without the ability to determine the cause of SIDS, it’s impossible to prevent. However, there are some known risk factors that can help guide prevention practices.

1. Back sleeping: The risk for SUID is considerably higher for infants who are placed on their stomach or sides when they sleep.

Always lay an infant on his or her back, especially during their first six months or until they’re able to roll over on their own. The American Pediatric Association also warns caregivers to follow this rule, as infants who are accustomed to back sleeping are 18 times more likely to die when placed on their stomach to sleep.

2. Sleep environment: Fluffy blankets, pillows, bumpers and stuffed animals can increase the risk of an accidental infant suffocation.

All infants should sleep on a firm mattress with a tightly fitted sheet — absolutely no additional padding, blankets or other accessories, including bumper pads.

3. Share a room, not a bed: Always return the infant to a crib before falling asleep, as co-sleeping can lead to accidental suffocation or smothering.

It is recommended to keep the crib or bassinet in the same room as you for the infant’s first six months, as the instances of SIDS decrease for infants who share a room with a parent.

4. Temperature: Overheating may increase the risk for SIDS, so be sure the infant isn’t overdressed or sleeping in a room that’s too warm.

If you’re worried about the infant getting cold during the winter, dress him or her in a onesie or a sleepsack, which is a wearable blanket.

5. Have a healthy pregnancy and smoke-free home: Smoking, drinking or using drugs during pregnancy can increase the risk of SUID.

KidsHealth Organization reports that SIDS is three times more likely in infants of mothers who smoked during pregnancy, and infants who are exposed to secondhand smoke have double the risk of SIDS compared with infants who are not.

6. Feeding: Breastfeeding is associated with decreased risk of SIDS.

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