Sudden Infant Death Syndrome (SIDS) is the unexpected, sudden death of an infant under one year of age that remains unexplained even after an autopsy and thorough medical investigation. SIDS is the leading cause of death in children between one month and one year of age, and in most cases the infant was believed to be healthy immediately before the death.

The risk for SIDS peaks between 2 and 3 months of age, and it occurs more often in male infants than in females. African American children are two to three times more likely than Caucasian children to die of SIDS, and Native American infants are three times more likely than Caucasians to succumb to SIDS. The annual incidence of SIDS has declined since 1992, a finding commonly attributed to the Back to Sleep Campaign.

While the cause of SIDS has not yet been discovered, some common factors that contribute to an increased risk of SIDS have been identified. They include:

Infant sleeping in the prone position (stomach sleeping)

Use of soft bedding or unsafe beds (couches, daybeds, waterbeds)

Use of loose bedding materials such as blankets and pillows

Overheating due to clothing, blankets or room temperature

Mother’s age younger than 20 years

Mother smoking during pregnancy

Mother receiving late or no prenatal care

Premature birth or low birth weight

Exposure to secondhand smoke

Research suggests that SIDS occurs when an infant’s body has difficulty regulating breathing, cardiovascular functions, and/or body temperature because of an underlying developmental delay or problem in parts of the brain controlling those activities. For example, some infants who succumb to SIDS are born with an abnormality in regions of the brain that control breathing and the normal arousal response. Infants born with other brain defects, possibly due to genetics, exposure to a toxic substance or lack of oxygen to the fetus (due to cigarette smoking during pregnancy, for example), may also be more susceptible to SIDS.

Scientists believe that while these developmental defects or delays alone may not cause SIDS, sudden infant death syndrome may occur when these vulnerabilities combine with other events, such as difficulty breathing due to an infection, decreased oxygen intake resulting from bedding that covers the infants face. For instance, infants who are sleeping on their stomachs and begin re-breathing air that is trapped in their bedding normally wake up and cry. An infant with a brain abnormality may not send the protective wake up signal. Similarly, an infant sleeping on his or her stomach whose head becomes covered by bedding may begin to overheat; while the brain usually triggers the infant to wake up and move to free his or her head, the overheating may inhibit the brains protective wake up signal.

To help explain the complex processes that may cause SIDS, The National Institute of Child Health & Human Development (NICHD) has put forward the “triple-risk hypothesis,” suggesting infants who die of SIDS are:

in a critical stage in the development of their immune, cardiovascular and respiratory systems

susceptible to risks during this stage due to an underlying muscular weakness or neurologic defect

affected by an environmental cause such as stomach sleeping or soft bedding

A seasonal component has also been noted in SIDS, as SIDS deaths tend occur more frequently during the winter months. This may be linked to using excess clothing and bedding in an attempt to keep infants warm, and to the increase in respiratory infections that occur during the winter.

Myths

Immunizations cause SIDS. There is no connection between immunizations and SIDS, according to a 2003 study by the Institute of Medicine’s (IOM) Board on Health Promotion and Disease Prevention.

Infants are at a greater risk for choking when sleeping on their backs. Doctors have found no increase in choking or other problems in infants who sleep on their backs.

Side sleeping is just as safe as back sleeping. Side sleeping is not as safe as back sleeping. Infants who sleep on their sides can roll onto their stomachs, putting them at a greater risk for SIDS.

It is never safe for an infant to be placed on his or her stomach. Infants can be placed on their stomachs when they are awake and someone is watching the child. This “tummy time” is good for the baby because it can help develop neck and shoulder muscles.

Sleeping on the back is unhealthy because it causes flattening of the back of the head. Flat spots on the back of the infant’s head tend to go away within a few months after he or she learns to sit up. Placing the baby on his or her stomach while awake and cuddling the baby in the upright position can also help reduce flat spots. Periodically changing the direction the babies head when he or she is put down is also recommended.

Symptoms

SIDS is the diagnosis given when an infant under one year of age dies suddenly, and the incident cannot be explained by recent illnesses, medical history, an autopsy or the death scene itself. Since SIDS is a diagnosis of exclusion, given when the investigation provides no other explanation, there is not a specific list of symptoms to determine whether a baby is in danger of succumbing to SIDS. However, risk factors have been identified and include:

Sleeping in the prone position (stomach sleeping)

Soft bedding or unsafe beds (couches, daybeds, waterbeds)

Loose bedding such as blankets and pillows

Overheating due to clothing, blankets or room temperature

Exposure to secondhand smoke

Mother smoking during pregnancy

Mother’s age younger than 20 years

Mother receiving late or no prenatal care

Premature birth or low birth weight

Recovering or having recently recovered from a respiratory or intestinal infection

Treatment

There is no treatment for SIDS. However, there are things that can be done to reduce the risk of SIDS. While the exact cause of SIDS is unknown, researchers have identified steps that can be taken to reduce the risk of SIDS. Starting during pregnancy, mothers can reduce their children’s risk of SIDS through frequent medical check-ups, proper nutrition and avoiding tobacco, alcohol and drug use.

When caring for an infant, the following steps can also reduce the risk of SIDS:

Place the baby to sleep on his or her back. Since the early 1990s, when the National Institutes of Health (NIH) and the American Academy of Pediatrics (AAP) began recommending that babies be placed on their backs to sleep, the number of SIDS fatalities has dropped by over 50 percent.

Make sure the baby sleeps on a firm mattress, in a safety-approved crib. Soft mattresses, sofas, waterbeds, sheepskins or other soft sleeping surfaces increase the risk of SIDS.

Remove soft, fluffy bedding, pillows and stuffed toys from the baby’s sleep area.

Make sure the baby’s head and face stay uncovered during sleep. If you do use a blanket, keep it away from the baby’s mouth and nose. To use a blanket, make sure the baby’s feet are at the bottom of the crib, that the blanket is no higher than the baby’s chest, and the blanket is tucked in around the bottom of the crib mattress.

Ensure that your baby does not become overheated. Keep the baby’s room at a temperature that is comfortable for adults, and avoid too many layers of clothing or blankets.

Offer a pacifier at nap time and bed time. Studies show that pacifiers may protect against SIDS. Pacifiers are recommended throughout the first year of life (and after one month of age for breast-fed infants). The pacifier should be used when placing the baby down to sleep, but should not be reinserted once the infant falls asleep. If the infant refuses the pacifier, he or she should not be forced to take it. Pacifiers should be cleaned regularly and should not be coated with sweet substances.

Do not allow smoking around your baby. Make sure all family members, babysitters and anyone else who cares for the infant knows these tips to reduce the risk of SIDS.

The American Academy of Pediatrics (AAP) recommends that infants sleep in a crib, bassinet or cradle in the same room as the parent. Commercial devices marketed to reduce the risk of SIDS should be avoided, according to the AAP, since they have not been sufficiently tested for safety and effectiveness. The AAP also cautions that home monitors should not be considered an effective strategy to reduce the risk of SIDS. While electronic respiratory and cardiac monitors may be used for infants deemed to have extreme cardiorespiratory instability or who have had an apparent life-threatening event involving apnea or other breathing difficulty, there is no evidence that using a home monitor reduces the incidence of SIDS.

Coping

Losing a child to SIDS is a tragedy that can cause intense reactions of disbelief, denial, confusion, guilt, anger and depression among parents and other family members. This depression often affects sleeping, eating, the ability to focus and overall energy level. Many parents experience unreasonable fears that other family members may also be in danger, and may over-protect surviving children or have fears for future children.

Surviving siblings may also fear that other family members will suddenly die, or they may feel guilty about the sibling’s death. Signs that children are suffering include increased clinging to parents, difficulties in school, misbehaving and disturbed sleep. It helps to talk to surviving children about the death, explaining that the baby died because of a medical problem that only occurs in infants.

Families who have lost an infant may benefit from counseling and support groups, such as services offered through the SIDS Alliance.

Reviewed by Daniel S. Lewin, Ph.D., D.ABSM, Director, Pediatric Behavioral Sleep Medicine, Children’s National Medical Center, and Assistant Professor of Pediatrics and Psychiatry, George Washington University School of Medicine.