Sudden Infant Death Syndrome (SIDS)

If you’re concerned that your child or grandchild is in danger of SIDS, it will comfort you to know that Boston Children’s Hospital has a tremendous amount of experience counseling parents on techniques to greatly reduce the risk.

What is SIDS?

Sudden infant death syndrome (SIDS) is the sudden and unexplained death of a baby younger than 1 year old. A diagnosis of SIDS is made if the baby’s death remains unexplained even after a death scene investigation, an autopsy, and a review of the clinical history.

SIDS is part of a larger category of unexpected (as opposed to unexplained) infant deaths called SUDI (sudden unexpected death in infancy). Babies who die suddenly but whose causes of death are later explained (infection, brain abnormality, cardiac dysfunction, etc.) also fall into this SUDI category.

Who is at risk for SIDS?

SIDS is a mysterious syndrome, since by its very definition the cause cannot be determined. But certain risk factors do exist.

About 2,300 babies in the United States die of SIDS each year. Some babies are more at risk than others. For example, SIDS is more likely to affect a baby who is between 1 and 4 months old, it is more common in boys than girls, and most deaths occur during the fall, winter and early spring months.

Factors that may place a baby at higher risk of dying from SIDS include the following:

• babies who sleep on their stomach or their side rather than their back
• overheating while sleeping
• too soft a sleeping surface, with fluffy blankets or toys
• mothers who smoke during pregnancy (three times more likely to have a baby with SIDS)
• exposure to passive smoke from smoking by mothers, fathers, and others in the household doubles a baby's risk of SIDS
• mothers who are younger than 20 years old at the time of their first pregnancy
• babies born to mothers who had little, late, or no prenatal care
• premature or low birth weight babies
• having a sibling who died of SIDS

Are there any theories about why SIDS occurs?

While the cause of SIDS is unknown, many clinicians and researchers believe that SIDS is associated with problems in the ability of the baby to arouse from sleep, to detect low levels of oxygen, or a buildup of carbon dioxide in the blood. When babies sleep face down, they may re-breathe exhaled carbon dioxide. Normally, rising carbon dioxide levels activate nerve cells in the brainstem, which stimulate the brain's respiratory and arousal centers. The baby then wakes up, turns his head, and breathes faster to get more oxygen. SIDS babies, however, may fail to rouse.

The “Triple-Risk Model” for SIDS has been proposed to explain how SIDS occurs. The model holds that SIDS occurs when three conditions exist simultaneously:

• the infant has an underlying (e.g., brainstem) abnormality that makes him unable to respond to low oxygen or high carbon dioxide blood levels
• the infant is exposed to a triggering event such as sleeping face down on its tummy
• these events occur during a vulnerable stage in the infant’s development, i.e., the first six months of life

How is SIDS diagnosed?

A baby is determined to have died from SIDS if no cause of death can be identified following a death scene investigation, an autopsy, and a review of the clinical history. Thus, SIDS is a diagnosis of exclusion: SIDS as a cause of death is determined only when all other causes have been excluded.

Can SIDS be prevented?

Because researchers at Children’s and elsewhere are still researching the possible causes of SIDS, there is currently no way to “prevent” the syndrome from occurring. But you can vastly reduce your baby’s risk of SIDS by:

• putting your baby to sleep on his back
• using a firm sleep surface and keeping fluffy blankets and stuffed animals out of his crib
• not overheating your baby or his room when he sleeps
• not smoking when you are pregnant and not allowing anyone to smoke around your baby
• breastfeeding

Causes of SIDS

SIDS is a mysterious syndrome, and by its very definition the cause cannot be determined. Children’s researchers have uncovered strong evidence that SIDS has a biological basis, and are continuing to work towards determining the underlying causes and identifying at-risk babies.

Who’s at risk

• babies who sleep on their stomachs
• premature or low birth weight babies
• babies who become overheated during sleep
• babies who sleep on too soft a surface, or who cribs have soft blankets and bumper pads
• babies who have a sibling who died of SIDS, or whose family history includes failure to thrive

Prevention

• place your baby on his back to sleep
• keep fluffy blankets and stuffed animals out of his crib
• don’t overheat the baby or his room when he sleeps
• don’t allow anyone to smoke around your baby
• breastfeed your baby

Parents’ smoking increases the risk of SIDS

Diseases caused by smoking kill almost a half-million people in the United States every year. Despite anti-smoking campaigns and medical warnings, more than 6,000 children and teens smoke their first cigarette each day — and half of those will become regular smokers. Pregnant moms who smoke increase their babies’ risk of SIDS. Quitting smoking is one of the best things you can do for your baby’s health — and your own.

How Boston Children's diagnoses Sudden Infant Death Syndrome (SIDS)

Currently, there is no diagnostic test available for SIDS. A diagnosis of SIDS is reached only when the cause of death remains unexplained after a death scene investigation, an autopsy and a review of the clinical history. Similarly, there is currently no way to predict babies that are at risk of SIDS.

How we address SIDS

There currently is no way of predicting which babies die from SIDS. However, early and regular prenatal care can help reduce the risk of SIDS. And there are many precautions that you can take to lower the risk of your baby dying from SIDS:

• Put your baby on his back while he sleeps.
  • Parents, babysitters, day care workers and other caregivers should always put babies to sleep on their backs, instead of on their stomachs.
  • Studies have shown that putting babies to sleep on their backs has reduced the number of SIDS cases by as much as a half.
  • Use other positions only if your doctor recommends that you do so. In some instances, doctors may recommend that babies be placed on their stomachs to sleep if they have certain disorders, such as gastroesophageal reflux or some upper airway disorders, which make babies more likely to have choking or breathing problems while lying on their backs.
     
• Place your baby on his tummy while he's awake.
  • A certain amount of time spent on the tummy while your baby is awake and being cared for is important for motor development of his shoulders.
  • “Awake time” spent on the stomach may help prevent flat spots from developing on the back of your baby's head.
     
• Make sure that your baby sleeps on a firm mattress or other firm surface.
  • Don't use fluffy blankets or comforters over or under your baby.
  • Don't let your baby sleep on a waterbed, sheepskin, a pillow, or other soft materials.
  • When your baby is very young, don't place soft stuffed toys or pillows in the crib with him. Some babies have smothered with these soft materials in the crib.
  • Don't place bumper pads around your baby's crib.
     
• Babies should be kept warm, but not too warm. An overheated baby is more likely to go into a deep sleep from which it is difficult for him to arouse.
   
• Bring your baby's crib into your room for the first six months, possibly because it's easier to monitor your baby when he sleeps in the same room as you.
   
• Avoid bed-sharing.
  • While bed-sharing may have certain benefits, there are no scientific studies demonstrating that bed-sharing reduces SIDS. Some studies suggest that bed-sharing, under certain conditions, may actually increase the risk of SIDS
     
• Make sure that your baby has a smoke-free environment.
  • Don't smoke when you're pregnant.
  • Don't let anyone smoke around your baby. Babies and young children exposed to smoke have an increased risk of SIDS, as well as more colds and other diseases.
     
• If your baby seems to be sick, call your doctor right away.
  • Parents should be sure to take their babies for their regular well-baby check-ups and routine immunizations.
     
• If possible, breastfeed your baby.
  • Evidence suggests that breastfeeding might reduce the risk of SIDS, for reasons that aren't fully understood.

Children's Infant Follow-Up Program

Children who are born prematurely benefit from special monitoring and intervention during their first years of life. Our Infant Follow-Up Program (IFUP) provides ongoing medical and developmental evaluation and support for very premature infants.

Our care is informed by our research, and our discoveries in the lab strengthen the care we provide at each child's bedside. In fact, our scientific research program is one of the largest and most active of any pediatric hospital in the world.

Currently, there is no way to identify living infants at risk of SIDS. But the development of such a test is a major goal of SIDS research at Children’s.

Among Children’s research projects that hold promise for preventing SIDS is research into a neurochemical abnormality in the brainstem that may be responsible for the failure of protective breathing, heart and arousal responses that are thought to be responsible for SIDS.

Recent autopsy data provide the strongest evidence yet that sudden infant death syndrome (SIDS) has a concrete biological basis. Children’s neuropathologist Hannah Kinney, MD, and colleagues have found that babies who die from SIDS have abnormalities in the brainstem, the part of the brain that controls breathing; that responds to re-breathing too much carbon dioxide; and that regulates blood pressure and body temperature — all of which are important in sleeping and waking.

Our researchers found that the brainstems of SIDS infants have lower levels of the neurochemical serotonin and a signaling protein called 14-3-3. They also had significantly fewer receptors for serotonin and another neurochemical gamma-amino-butyric acid (GABA). These abnormalities are thought to prevent SIDS infants from properly controlling the vital functions that keep them alive and ultimately to lead to their death.

Dr. Kinney and colleagues are currently working towards a means of identifying those infants who are at increased risk of SIDS, with the ultimate goal of developing a treatment that will protect them from SIDS.