What is Sudden Infant Death Syndrome (SIDS)?

SIDS is the diagnosis given for the sudden death of an infant under one year of age that remains unexplained after a complete investigation, which includes an autopsy, examination of the death scene (Center for Disease Control and Prevention guidelines), and review of the symptoms or illnesses the infant had prior to dying and any other pertinent medical and family history. SIDS is sometimes called "crib death," however, according to the Chicago Infant Mortality Study, the vast majority (75 - 80%) of babies who die from SIDS in Chicago are not sleeping in cribs.  Cribs do not cause SIDS, however, other aspects of an infant’s sleep environment have been associated with increasing the risks for SIDS. 

What causes SIDS?

There is mounting evidence that suggests some SIDS babies are born with brain abnormalities that make them vulnerable to sudden death during infancy.  Studies of SIDS victims reveal that many SIDS infants have abnormalities in the "arcuate nucleus," a portion of the brain that is involved in control of breathing and waking during sleep.  Babies born with defects in other portions of the brain or body may also be more prone to a sudden death.  These abnormalities may stem from prenatal exposure to a toxic substance, or lack of a vital compound in the prenatal environment, such as sufficient oxygen.

When is SIDS most likely to occur?

SIDS is the leading cause of death in infants between one to 12 months old.  Most SIDS deaths occur when a baby is between 2 and 4 months of age.  The risk of SIDS then diminishes during the first year of life.  Currently, the diagnosis of SIDS is not used after 1 year of age.  SIDS rates are higher during the colder months of the year.

Is there anything we can do to prevent SIDS?

At this time, there is no way of predicting which newborns will succumb to SIDS.  However, there are a few measures parents can take to lower the risk of their child dying from SIDS in order to give their infant the best possible chance to thrive.

Back Sleeping.  Placing babies on their backs to sleep is the single most important step that parents and other caregivers can take to reduce the risk of SIDS.  Infants who fall asleep on their stomachs should be gently turned onto their backs.  Studies have shown that countries where caregivers have switched from placing babies on their stomachs to sleep to placing babies on their backs to sleep have reduced their total SIDS deaths by as much as 70 percent. 2,000 fewer infants die of SIDS in the U.S. each year due to this simple measure.

Bedding.  Parents should make sure their baby sleeps on a firm, flat mattress in a crib that meets current safety standards.  Caregivers should also avoid using loose, fluffy blankets or coverings and should not use pillows, sheepskins or comforters under the baby. Consider using a sleeper or other sleep clothing as an alternative to blankets, with no other covering.  Infants under 1 year of age should not be placed to sleep on a waterbed, sofa or with stuffed toys or pillows.

Head Covering.  Make sure your baby’s head remains uncovered during sleep.  Babies are at an increased risk for SIDS if their head becomes covered during sleep.  Avoid using a blanket or other covering over your baby’s face as a sun or weather screen, or to block out distractions or sounds while your baby is sleeping.  Bedding that bunches up or contours around your baby’s face can obstruct the mouth and nose, causing potentially dangerous re-breathing of stale air.  If using a blanket in a crib, put the baby’s feet to the foot of the crib and tuck the blanket under the mattress so that the baby cannot pull the blanket over his head.

Bedsharing/Sofa-sharing.  In addition to the recognized hazards presented by pillows and comforters in the family bed, there are risks associated with infants who sleep with parents whose instincts are impaired by exhaustion, drug or alcohol abuse, or who are smokers.  There are also dangers connected with infants sharing a bed with brothers, sisters, or relatives other than the baby’s mother.  Sofas and chairs are particularly dangerous environments for shared sleep.  Bedsharing has not been found to be protective against SIDS, though studies suggest that room-sharing may be protective.  Keeping the baby next to the adult bed in her own secure crib or bassinet provides greater safety for the infant and proximity for parents seeking to facilitate breastfeeding and share closeness with their baby.

Smoking.  Mothers who smoke during pregnancy are three times more likely to have a SIDS baby, and exposure to passive smoke from smoking by mothers, fathers, and others in the household after pregnancy doubles a baby's risk of SIDS.  Parents should be sure to keep their babies in a smoke-free environment.  Studies have found that the risk of SIDS rises with each additional smoker in the household, the numbers of cigarettes smoked a day, and the length of the infant’s exposure to cigarette smoke.  Components of smoke are believed to interfere with an infant’s developing lungs and nervous system, and to disrupt a baby’s ability to wake from sleep.

Room Temperature.  Babies should be kept warm, but they should not be allowed to get too warm.  An overheated baby is more likely to go into a deep sleep from which it is difficult to arouse.  Keep the temperature in the baby's room at a level that feels comfortable to an adult and avoid overdressing the baby.    

Prenatal Care.  Good prenatal care – including proper nutrition, abstinence from alcohol, drugs, and smoking, and frequent medical checkups beginning early in pregnancy – might help prevent a baby from developing an abnormality that could put him or her at risk for sudden death. 

Regular Health Care.  Parents should take their babies to their health care provider for regular well baby checkups, and should make sure that their babies receive their immunizations on schedule.  The National Institutes of Health have turned up no connection between immunizations and SIDS.  In fact, SIDS occurs among infants who never received their shots, as well as in countries with different immunization schedules.

Child Care.  Babies who routinely sleep on their backs and are unaccustomed to sleeping on their stomachs are at an 18 times higher risk of SIDS when placed prone by a well-intentioned but ill-informed relative or caregiver.  Studies tell us that a disproportionate number of SIDS deaths are occurring in family day care settings.  This is not so surprising when coupled with the fact that half of family day care providers are over 50 years of age, have school-aged or older children, and have not received SIDS risk reduction education.  Be sure to communicate Back to Sleep advisories to baby sitters, daycare providers, grandparents and everyone else who cares for your infant.  Parents cannot assume that everyone knows about Back to Sleep and other ways to reduce SIDS risk.

What is the Back to Sleep campaign?   

Back to Sleep is aptly named for its main recommendation to place healthy infants on their backs to sleep to reduce the risk of SIDS.  The National Institute of Child Health and Human Development (NICHD) leads the campaign, along with the Maternal and Child Health Bureau and other Federal agencies such as the Centers for Disease Control and the Census Bureau.  The American Academy of Pediatrics (AAP) is the major private sponsor, along with the SIDS Alliance and the Association of SIDS and Infant Mortality Programs.  Based on a recommendation made by the AAP in 1992, the campaign was launched in 1994 with an effort to reach every newborn nursery in the country.  In March 1997, Tipper Gore became national campaign spokesperson.

Is the campaign successful?

This campaign has been increasingly successful in reaching parents and other caregivers of infants.  We have seen a change from 70 percent of babies placed on their stomachs to sleep in 1992 to 21 percent in 1998.  In Spring of 1999, NICHD phone surveys in Cook County indicated only 11% of infants were placed on their stomachs to sleep.  The death rate from SIDS declined nationally by 42% between 1992 and 1998, the first significant decrease in SIDS deaths in the U.S.

 Are there any infants that are more at risk for SIDS?

Yes, infants in the following categories are at a statistically higher risk for SIDS:

<     Infants born to mothers who are less than 20 years old at the time of their first pregnancy

<     Boys are more likely to die from SIDS

<     Babies born to mothers who had no or late prenatal care

<     Infants born to mothers with too short an interval between pregnancies

<     Premature or low birth weight babies and multiples

<     Babies born to mothers who smoke during or after pregnancy

<     Infants who are placed to sleep on their stomach

Are any ethnic groups more prone to SIDS?

Illinois’ African American infants are more than four times more likely to die of SIDS than white infants.  The Back to Sleep campaign is being stepped up, with a special effort to get the message out to these and other previously underserved populations with the help of community, civic and religious groups.

Is SIDS inherited?

There may be something that genetically predisposes an infant to higher SIDS risk.  Metabolic disorders, which can be inherited, have, at times, been mistaken for SIDS.  One such disorder, medium chain acylCoA dehydrogenase deficiency (MCAD), prevents an infant from properly processing fatty acids.  A build up of these acid metabolites could eventually lead to a rapid and fatal disruption in breathing and heart functioning.  If there is a family history of this disorder or childhood death of unknown cause (especially more than one case within a family), genetic screening of parents by a blood test can determine if they are carriers of this disorder.  If one or both parents is found to be a carrier, the baby can be tested soon after birth at little cost.  This is another reason why the autopsy is so important.  Tests can be done on the tissues of an infant to identify known metabolic disorders.  Illinois’ Department of Public Health will begin testing for these metabolic disorders as part of their newborn screening  sometime during the next year.

I have heard that the side sleep position is effective against SIDS.

In 1992, the American Academy of Pediatrics (AAP) recommended both the side and the back sleeping position to reduce the risk of SIDS.  In 1996, however, after reviewing data from various new studies, they revised their recommendation to back sleeping as the best position for infants.  These reports indicated that the risk for SIDS is greater for babies placed on their sides versus those placed on their backs, perhaps because babies placed on their sides have a higher likelihood of spontaneously turning onto their tummies.  However, both back and side positions are associated with a much lower risk for SIDS than stomach sleeping.  If the side position is used, caretakers should be advised to bring the dependent arm forward to lessen the likelihood of the baby rolling onto its tummy.

 Won’t my baby choke on spit-up or vomit during sleep if placed on its back?

 Many parents place babies on their stomachs to sleep because they think it prevents them from choking on spit-up or vomit during sleep.  But studies in countries where there has been a switch from babies sleeping predominantly on their stomachs to sleeping mainly on their backs have not found any evidence of increased incidence of aspiration, pneumonia, choking, or other problems.  In addition, the AAP has reviewed all the scientific literature and found that there is no additional risk of choking on vomit when babies sleep on their backs.

Which babies should not be placed on their backs to sleep?

In some instances, doctors may recommend that babies be placed on their stomachs to sleep if they have disorders such as gastroesophageal reflux or certain upper airway disorders that predispose them to choking or breathing problems while lying on their backs.  If parents are unsure about the best sleep position for their baby, it is always a good idea to talk to the baby's doctor or other health care provider.

Doesn’t back sleeping cause flat heads?    

There is some suggestion that the incidence of babies developing flat spots may have increased with back sleeping.  This is almost always a benign condition, which will disappear within several months after the baby has begun to sit up.  Flat spots can be avoided by altering the back sleeping head position, such as turning the head to one side for a week or so and then changing to the other.  Reversing the head-to-toe axis in the crib so the baby’s head can continually face outside activity (e.g., the door to the room) helps maintain this position.

Should infants ever be placed on their tummies?

A certain amount of "tummy time" while the infant is awake and being observed is recommended for motor development of the shoulder. In addition, supervised awake time on the stomach may help prevent flat spots from developing on the back of the baby's head.

What if my baby cries and cries and won’t sleep in the back position?

Positional preference appears to be a learned behavior among infants from birth to 4 to 6 months of age.  Infants who start out sleeping on their backs from day one should become accustomed most readily to the back sleeping position.  However, if you are having great difficulty with your infant, try turning him over to his back after he has fallen asleep.  If that doesn’t help, consider the side position, with your baby’s lower arm extended forward to stop him or her from rolling over onto the stomach.  While the side position does not provide as much protection against SIDS as back sleeping, it is still much better than placing your baby on his or her tummy.

Could a pacifier protect a baby against SIDS?

There have been a few studies done on the relationship between SIDS and pacifiers.  In each case, it appears that the use of pacifiers is associated with a decreased risk of SIDS.  There are many possibilities for this finding.  Some researchers have suggested that a pacifier may prevent the infant’s tongue from falling back into the throat causing the air passage to seal.  Others have theorized that pacifiers encourage swallowing and therefore stimulate the muscular development of upper airways; or that pacifier use prevents an infant from turning into a directly prone position.  Until further studies explain the relationship between pacifier use in infants and SIDS, the Back to Sleep campaign does not make a recommendation for or against their use.  Parents and child care providers are, however, to be discouraged from taking a pacifier away from a baby who seems to need or want one.

Should sleeping “wedges” be used for infants?

The American Academy of Pediatrics has stated that devices designed to maintain sleep position are not recommended since they have not been sufficiently tested for their safety and none have been shown to be effective at reducing the risk of SIDS.

Are there any advantages or disadvantages to “shared sleeping” arrangements?

Scientific studies have demonstrated that bedsharing, between baby and mother, can alter sleep patterns of mother and baby.  These studies have led to a speculation in the lay press that bedsharing or “co-sleeping” may also reduce the risk of SIDS.  While bedsharing may have certain benefits (such as encouraging breast feeding), there are no scientific studies demonstrating that bedsharing reduces SIDS.  Conversely, there are studies suggesting that bedsharing, under certain conditions, may actually increase the risk of SIDS.  There is no basis at this time for encouraging bedsharing as a strategy to reduce SIDS risk.  However, studies indicate that room-sharing – keeping the baby alongside the adult bed in his own crib or bassinet – may be protective against SIDS.

Is there any research on home monitors?

Among the many avenues of research initiated by the NICHD, infant monitoring was thoroughly investigated by NICHD-funded researchers.  In the 1970's and early 1980's, it was thought that monitoring had promise in identifying infants at risk for SIDS and signaling caregivers when infants have life-threatening events that may proceed to SIDS. In September of 1986, the NICHD held a consensus conference titled, "Infantile Apnea and Home Monitoring."  After examining all available research, the consensus panel determined that cardiorespiratory monitoring is effective only in managing apnea.  For the normal newborn, the risks, disadvantages, and costs of monitoring outweigh the potential of identifying infants at risk for SIDS.

Does NICHD recommend the use of monitors to prevent SIDS?

Although some electronic home monitors detect and sound an alarm when a baby stops breathing, there is no evidence that such monitors prevent SIDS.  The monitors also pose several disadvantages, including frequent false alarms, restricted mobility of both infant and parents, and the risk of electrical injury to young children.

A panel of experts convened by the National Institutes of Health recommended that home monitors not be used for babies who do not have an increased risk of sudden unexpected death.  However, the monitors may be recommended in some cases in which infants have experienced one or more severe episodes during which they stopped breathing and required resuscitation or stimulation, if the baby is premature and has symptomatic apnea, or if the baby has a medical condition such as central hypoventilation.  If an incident has occurred or if an infant is on a monitor, parents need to know how to properly use and maintain the device, as well as how to resuscitate their baby if the alarm sounds.

Excerpted and edited by the SIDS Alliance  -- August 2000