Sudden Infant Death Syndrome (SIDS)

Sudden infant death syndrome (SIDS) is the sudden and unexplained death of a baby under 1 year of age. It is the major cause of death in babies from 1 month to 1 year of age. The death is sudden and unpredictable; in most cases, the baby seems healthy.

Death occurs quickly, usually during a sleep time.

After 30 years of research, scientists still cannot find any definite causes for SIDS. Although there is no way to predict or prevent SIDS, research has found some things that can help reduce the risk of SIDS.

Evidence has shown that some babies who die from SIDS are born with brain abnormalities that make them vulnerable to sudden death during infancy. Studies of SIDS victims show that many SIDS babies have abnormalities in the "arcuate nucleus," a part of the brain that probably helps control 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 result from exposure of the fetus to a toxic substance, or a decrease in oxygen. Cigarette smoking during pregnancy, for example, can reduce the amount of oxygen the fetus receives.

Events such as lack of oxygen, excessive carbon dioxide intake, overheating, or an infection may be related to SIDS. Examples of a lack of oxygen and excessive carbon dioxide levels may include:

  • Respiratory infections that cause breathing problems
  • Rebreathing exhaled air trapped in underlying bedding when babies sleep on their stomachs

Normally, babies sense when they do not get enough air and the brain triggers the babies to wake from sleep and cry. This changes their heartbeat or breathing patterns to make up for the lowered oxygen and excess carbon dioxide. A baby with a flawed arcuate nucleus, however, might lack this protective mechanism.

This may explain why babies who sleep on their stomachs are more susceptible to SIDS, and why a large number of SIDS babies have been reported to have respiratory infections prior to their deaths. This may also explain why more SIDS cases occur during the colder months of the year, when respiratory and intestinal infections are more common.

The numbers of cells and proteins made by the immune system of some SIDS babies have been reported to be higher than normal. Some of these proteins can interact with the brain to change heart rate and breathing during sleep, or can put the baby into a deep sleep. Such effects might be strong enough to cause the baby's death, particularly if the baby has an underlying brain defect.

Some babies who die suddenly may be born with a metabolic disorder. One such disorder is medium chain acyl-CoA dehydrogenase deficiency, which prevents the baby from properly processing fatty acids. A build-up of these acid metabolites could eventually lead to a rapid and fatal interruption in breathing and heart functioning. If there is a family history of this disorder or childhood death of unknown cause, genetic screening of the 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.

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 when a baby is between 1 and 4 months old. Factors that may place a baby at higher risk of dying from SIDS include:

  • Babies who sleep on their stomachs rather than their backs
  • Mothers who smoke during pregnancy (three times more likely to have a SIDS baby)
  • 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 no or late prenatal care
  • Premature or low birthweight babies

The diagnosis of SIDS is given when the cause of death remains unexplained after a complete investigation, which includes:

  • An autopsy
  • Examination of the death scene
  • Review of the symptoms or illnesses the infant had prior to dying
  • Any other pertinent medical history

There currently is no way of predicting which babies will die from SIDS. However, there are a few measures parents can take to lower the risk of their baby dying from SIDS:

Prenatal Care

Early and regular prenatal care can help reduce the risk of SIDS. Proper nutrition, no smoking or drug or alcohol use by the mother, and frequent medical check-ups beginning early in pregnancy might help prevent a baby from developing an abnormality that could put him or her at risk for sudden death. These measures may also reduce the chance of having a premature or low birth weight baby, which also increases the risk for SIDS. The risk of SIDS is higher for babies whose mothers smoked during pregnancy.

Put Your Baby on His or Her Back for Sleep

Parents and other caregivers should put babies to sleep on their backs as opposed to on their stomachs or sides. Studies have shown that placing babies on their backs to sleep has reduced the number of SIDS cases by as much as a half in countries where babies had traditionally slept on their stomachs. Babies who can roll from their back to their belly and from their belly to their back on their own can be left in that position.  Move your baby to the crib or bassinet as soon as possible, if he or she falls asleep in a car safety seat, stroller, swing, infant sling or infant carrier.

Parents need to be sure that other caregivers, babysitters, family members and day care centers understand: 

    • SIDS 
    • SIDS risks 
    • What they can do to prevent SIDS

Although many parents are afraid babies will choke on spit-up or vomit if placed on their backs, studies have not found any evidence of increased risk of choking or other problems.

Use Other Positions Only with Physician Recommendations

In some instances, physicians may recommend that babies be placed on their stomachs to sleep if they have disorders such as gastroesophageal reflux or certain upper airway disorders, which make them more likely to have choking or breathing problems while lying on their backs.

Place Baby on Stomach while Awake

A certain amount of tummy time while the infant is awake and being observed is recommended for motor development of the shoulders. In addition, awake time on the stomach may help prevent flat spots from developing on the back of the baby's head. Such physical signs are almost always temporary and will disappear soon after the baby begins to sit up. 

Proper Bedding

Make sure that your baby sleeps on a firm mattress or other firm surface, such as a crib, bassinet, portable crib or play yard.  Do not use fluffy blankets or comforters under the baby. Do not let the baby sleep on beds (especially waterbeds), sofas, chairs, sheepskin pillows or other soft materials. When your baby is very young, do not place soft stuffed toys, bumper pads or pillows in the crib with him or her. Some babies have smothered with these soft materials in the crib. You may check with the Consumer Product and Safety Commission web site for more information about crib safety standards.

Temperature Control

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. The temperature in the baby's room should feel comfortable to an adult, and overdressing the baby should be avoided. Keep the temperature in your baby's room so that it feels comfortable to you.

Avoid Bed Sharing

Room sharing, but not bed sharing, is recommended.  There is evidence that this arrangement decreases the risk of SIDS as much as 50 percent.  Recently, scientific studies have shown that bed sharing between mother and baby, and others, can alter sleep patterns of the mother and her baby. Devices which claim to make bed sharing “safe,” such as co-sleepers or positioners, are not recommended. If a mother chooses to sleep in the same bed with her baby, although not recommended, care should be taken to avoid using soft sleep surfaces. Quilts, blankets, pillows, comforters or other similar soft materials should not be placed under the baby. Do not smoke or use substances such as alcohol or drugs, which may make waking difficult. It is also important to be aware that unlike cribs, which are designed to meet safety standards for babies, adult beds are not designed for a baby, and may carry a risk of accidental entrapment and suffocation.

Smoke-Free Environment

Do not smoke when you are pregnant and do not let anyone smoke around your baby. Keep your entire home and all of your cars and other vehicles smoke-free to protect your baby. Babies and young children exposed to smoke have more colds and other diseases, as well as an increased risk of SIDS. 

Pediatric Healthcare

If your baby seems sick, call your physician or clinic right away. Parents should take their babies for regular well-baby check-ups and routine immunizations. Claims that immunizations increase the risk of SIDS are not supported by research, and babies who receive their scheduled immunizations are less likely to die of SIDS. If a baby ever has an incident where he or she stops breathing and turns blue or limp, the baby should be medically evaluated for the cause of such an incident.

Breastfeed Your Baby

If possible, you should breastfeed your baby. There is evidence to suggest that breastfeeding might reduce the risk of SIDS. A few studies have found SIDS to be less common in babies who have been breastfed. This may be because breast milk can provide protection from some infections that can trigger sudden death in babies. If you bring your baby into your bed for feeding or comforting, you should return your baby to its crib when you are ready to return to sleep.

Consider a Pacifier at Bedtime and Nap Time

Scientific studies have shown a protective effect of pacifiers on reducing the risk of SIDS.  Offer a pacifier to your baby when placing the baby down to sleep.  You don’t have to replace the pacifier once the baby falls asleep. To avoid strangulation or other injuries, do not hang the pacifier around your baby’s neck or attach it to clothing while your baby is sleeping.  If you are breastfeeding, wait until breastfeeding is going well before offering a pacifier; this may take several weeks.

Home Monitors for Babies at Risk

Although some electronic home monitors can detect and sound an alarm when a baby stops breathing, there is no evidence that such monitors can prevent SIDS. In 1986, 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. The monitors may be recommended, however, for babies who have experienced one or more severe episodes during which they stopped breathing and required resuscitation or stimulation, premature babies with apnea (stopping breathing), and siblings of two or more SIDS babies. If an incident has occurred, or if a baby 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.

Cincinnati Children's Hospital Medical Center recommends the following resources for more information about sudden infant death syndrome (SIDS).

A comparison of healthy infants with those at increased risk for sudden infant death syndrome (SIDS) finds that events such as apnea and below-normal heart rate are common, even in healthy-term infants. But extreme cardiorespiratory events are common only among preterm infants, and their timing suggests they are not likely to be immediate precursors of SIDS. 


Last Updated 09/2012