What is sudden infant death syndrome (SIDS)?

Sudden infant death syndrome (SIDS) is the sudden and unexplained death of an infant baby under 1 year of age. SIDS is sometimes called crib death because the death occurs when a baby is sleeping in a crib. 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.

What causes SIDS?

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 have the following:

• brain abnormalities
  Some SIDS babies 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 after birth
  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 the following:
  
  
  • 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.
  
  

• immune system problems
  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.



• metabolic disorder
  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.

Who is at risk for SIDS?

About 5,000 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, 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 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

How is SIDS diagnosed?

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

• an autopsy
• examination of the death scene
• review of the symptoms or illnesses the infant had prior to dying
• any other pertinent medical history

What can be done to decrease the risk of SIDS?

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, including the following:

• 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/her at risk for sudden death. These measures may also reduce the chance of having a premature or low birthweight 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/her back for sleep
  Parents and other caregivers should put babies to sleep on their backs as opposed to on their stomachs. 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. Although babies placed on their sides to sleep have a lower risk of SIDS than those placed on their stomachs, the back sleep position is the best position for babies from 1 month to 1 year. Babies positioned on their sides to sleep should be placed with their lower arm forward to help prevent them from rolling onto their stomachs.
  
  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 his/her 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. Do not use fluffy blankets or comforters under the baby. Do not let the baby sleep on a waterbed, sheepskin, a pillow, or other soft materials. When your baby is very young, do not place soft stuffed toys or pillows in the crib with him/her. Some babies have smothered with these soft materials in the crib.



• 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
  Recently, scientific studies have shown that bed sharing between mother and baby can alter sleep patterns of the mother and her baby. While bed sharing may have certain benefits (such as encouraging breastfeeding), 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. If a mother chooses to sleep in the same bed with her baby, 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. 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 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/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.



• 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.

Are there any support groups for families who have experienced SIDS?

A SIDS death is a tragedy that affects family members and others as well. There are many support groups available that are experienced in helping families cope with a loss and work through their emotions associated with grieving. Consult your healthcare provider for recommended support groups in your community.