Children's Hospital Colorado

Sudden Infant Death Syndrome (SIDS)

What is SIDS?

A woman holds a baby wearing a diaper.

Sudden Infant Death Syndrome (SIDS) is the sudden and unexplained death of an infant who is younger than 1 year old. SIDS is the leading cause of death among infants 1 month to 1 year old, and claims the lives of about 2500 babies each year in the United States. In Colorado, between 50 and 80 babies have died from SIDS each year since 2004.

Despite years of research, doctors don’t know why SIDS strikes some infants. SIDS causes death without warning, usually in seemingly healthy babies, which can be very frightening to parents. SIDS deaths happen while babies are sleeping, and infants who die of SIDS show no signs of suffering.

While most conditions or diseases are diagnosed by the presence of specific symptoms, the diagnosis of SIDS comes only after all other possible causes of death have been ruled out through a review of the infant's medical history, sleeping environment and autopsy. This review helps distinguish true SIDS deaths from those resulting from accidents, abuse and undiagnosed medical conditions, such as cardiac or metabolic disorders.

What causes SIDS?

Unfortunately, we still don’t know what ultimately causes death from SIDS. However, we do know many of the factors in a baby’s sleep environment can put them at higher risk for SIDS.

After many years of research, the American Academy of Pediatrics (AAP) has released updated recommendations on what parents can do to make their baby’s sleep environment safer and lower their baby’s risk for SIDS.

Who gets SIDS?

The ultimate cause of SIDS is still unknown. It can happen to any baby less than 1 year old, even those who seem completely healthy and normal. Several factors combined may contribute to cause an at-risk infant to die of SIDS.

Most deaths due to SIDS occur in babies between 2 and 4 months of age, and the rate of SIDS increases during cold weather months. African American infants are twice as likely and Native American infants about three times more likely to die of SIDS than white infants. SIDS is more common in boys than girls.

These are the most important factors to AVOID because they put babies at significantly higher risk for SIDS:

  • Stomach sleeping
  • Sleeping on a sofa, adult bed or other soft surface
  • Sleeping in the same bed with someone else, including a parent or sibling (called “co-sleeping” or “co-bedding”)
  • Overheating from excessive sleepwear or blankets
  • Covering the baby’s head
  • Loose bedding, blankets or stuffed animals in the crib
  • Prematurity (more than 3 weeks early)
  • Low birth weight (less than 5 lb 8 oz)
  • Maternal smoking, drinking or drug use during pregnancy
  • Poor prenatal care
  • Young maternal age (mothers younger than 20)
  • Exposure to tobacco smoke after birth
  • Not breastfeeding
  • Recent respiratory illness

More about stomach sleeping risks

The biggest single risk factor for SIDS is stomach sleeping. Numerous studies show babies placed on their stomachs have a higher rate of SIDS than babies who sleep on their backs. Some researchers think that stomach sleeping puts pressure on a child's jaw, narrowing the airway and making breathing more difficult.

Another theory is that stomach sleeping can increase an infant's risk of "rebreathing" exhaled air, particularly if the infant is sleeping on a soft mattress or with bedding, stuffed toys or a pillow near the face. These soft surfaces may create a small enclosure around the baby's mouth and trap exhaled air. As a baby breathes exhaled air, the available oxygen level in the body drops. Eventually, this lack of oxygen could contribute to SIDS.

A third possibility is that infants who succumb to SIDS may have an abnormality in the part of the brain that controls breathing and helps the baby awaken during sleep. If a baby is not getting enough oxygen, the brain should trigger the baby to wake up and cry. But a problem with the breathing center in the brain could prevent the baby from having this normal reaction, and put him or her at greater risk for SIDS.

How do you prevent SIDS?

Because we don’t know exactly what causes SIDS, we don’t know how to completely prevent it. However, we do know several steps that parents and other caregivers can take to lower a baby’s risk of SIDS. The most important of these is to make sure you put your baby on his or her back to sleep. Putting a baby to sleep on their side is NOT a safe alternative to sleeping on their back because they often accidentally roll from their side to their stomach, increasing their risk for SIDS.

The evidence that links stomach sleeping to SIDS led the American Academy of Pediatrics (AAP) to recommend in the 1992 “Back to Sleep” campaign to ensure that all healthy infants younger than 1 year of age be put to sleep on their backs. Since the AAP's recommendation, the rate of SIDS has dropped by more than 50%.

Many parents fear that babies put to sleep on their backs could choke on spit-up or vomit. According to the AAP, however, there is no increased risk of choking for healthy infants who sleep on their backs.

Some parents may also be concerned about their infant developing a ‘flat head,’ called positional plagiocephaly, from spending too much time lying on their backs. Because back sleeping has become the norm, this condition has become quite common, but it is easily treatable by changing your baby's position frequently and spending "tummy time" while he or she is awake and supervised.

Once babies can roll over consistently, usually around 4 to 7 months, they may choose not to stay on their backs all night long. At this point, it is still recommended to put them down to sleep on their backs, but if they roll over on their own, it’s fine to let them stay in their own sleep position.

In addition to placing healthy infants on their backs to sleep, follow these steps to help reduce your baby’s risk of SIDS:

  • Place your baby on a firm mattress to sleep, never on a pillow, waterbed, sheepskin, couch, chair or other soft surface.
  • Do not put blankets, comforters, stuffed toys or pillows in the crib with the baby.
  • Do not use bumper pads in cribs. Bumper pads cause a risk of suffocation or strangulation if the baby rolls up with his face against the pad or accidentally gets loose bumper ties around his neck.
  • Babies should sleep in their own crib or bassinet in the same room with their parents. While infants can be brought into a parent's bed for nursing or comforting, parents should return the baby to the crib or bassinet when the baby is ready to sleep.
  • Make sure your baby receives all recommended immunizations. Studies have shown that routine immunization can reduce the risk of SIDS by 50%.
  • Make sure your baby does not get too warm while sleeping. Keep the room at a temperature that feels comfortable for an adult in a short-sleeve shirt.
  • Do not put your baby down to sleep wearing a hat.
  • Do not smoke, drink or use drugs while pregnant.
  • Do not expose your baby to secondhand smoke.
  • Receive early and regular prenatal care.
  • Make sure your baby has regular well-baby checkups.
  • Breastfeed if at all possible. Researchers think that breast milk may help protect babies from infections that increase the risk of SIDS.
  • If your baby has reflux, be sure to follow your doctor's guidelines on feeding and sleep positions.
  • Put your baby to sleep with a pacifier during the first year of life. Pacifiers have been linked with lower risk of SIDS. If your baby rejects the pacifier, don't force it.

Listen to one of our sleep experts, Dr. Ann Halbower, talk about the best ways to keep your child safe while sleeping.

Helpful resources

  • First Candle provides information and resources for caregivers and healthcare providers, as well as support services for families affected by SIDS across the United States.
  • American SIDS Institute provides information and resources as well as opportunities to work in SIDS reduction around the United States.
  • HealthyChildren.org is updated with the American Academy of Pediatrics’ most recent recommendations on the best way to reduce your child’s risk of SIDS.

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