Unknown: Sudden Infant Death Syndrome

views updated

Unknown: Sudden Infant Death Syndrome

Causes and Symptoms
The Future
For more information


Sudden infant death syndrome, or SIDS, is the unexpected death of an apparently healthy baby. According to the Centers for Disease Control and Prevention (CDC), such a death “cannot be explained after a thorough investigation is conducted, including a complete autopsy, examination of the death scene, and review of the baby's clinical history.”


In the typical SIDS case, the parents or caregivers put the baby to bed after feeding him or her. A check of the baby shortly after bedtime indicates that everything is normal. However, the baby is later found dead, usually in the position in which he or she had been placed at bedtime or naptime.

In most cases of SIDS, the parents state that the child was apparently healthy. However, some parents of infants who died of SIDS state that their babies “were not themselves” in the hours before death. In a number of cases, the parents report that the baby had diarrhea and vomiting at some point in the two weeks prior to death. Currently, doctors do not know whether these digestive problems are related to SIDS in some way or are only coincidental.


According to the CDC, SIDS is the leading cause of death among American infants between the ages of one and twelve months, and is the third leading cause overall of infant mortality in the United States. SIDS is

responsible for about one death per 2,000 live births as of the early 2000s; however, this figure is more than 50 percent lower than the figures for 1990, largely as a result of the “Back to Sleep” campaign.

Most SIDS deaths occur in babies between two and four months of age; only 1 percent occur in newborns. Boys are more likely than girls to die of SIDS; 60–70 percent of SIDS cases involve boys.

According to NICHD, African American babies are twice as likely as Caucasian babies to die from SIDS, and Native American babies are three times as likely. The reason for these differences is not yet known but may be related to other risk factors listed below.

Studies indicate that some mothers are at increased risk of having their child die of SIDS:

  • Those who smoke during pregnancy and after childbirth.
  • Those who abuse drugs or alcohol.
  • Those who are underweight or suffer from malnutrition.
  • Those who have children less than one year apart.
  • Teenage mothers. The more children the mother has while still in her teens, the greater the risk of SIDS.
  • Those who are obese.

“Back to Sleep” Campaign

The “Back to Sleep” Campaign is a safety program promoted by the National Institute of Child Health and Human Development (NICHD) that recommends placing a baby on its back for naps and sleeping at night. The campaign was started in 1992 following a recommendation from the American Academy of Pediatrics that babies should not be placed on their stomachs to sleep—as had been common practice for many years.

The Back to Sleep campaign emphasizes three central points:

  • Sleeping on the back reduces an infant's risk of sudden infant death syndrome (SIDS).
  • The sleeping surface makes a difference. Babies who are put to bed on a soft surface are at increased risk of SIDS.
  • Every sleep and nap time matters. Babies should always be placed on the back for sleeping. According to the campaign, “Babies who usually sleep on their backs but who are then placed on their stomachs are at very high risk for SIDS.”

Apart from sleeping position, some babies are at increased risk of SIDS:

Babies who are born prematurely.

  • Babies who weigh 4 pounds (1800 grams) or less at birth.
  • Babies who are not breastfed.
  • Babies who are part of a set of twins, triplets, or quadruplets.
  • Babies who are exposed to tobacco smoke.
  • Babies put to sleep in an overheated room.
  • Babies whose parents practice co-sleeping (the baby shares the parents’ bed at night).
  • Babies who are overdressed for sleep or covered with too many blankets.

Causes and Symptoms

The cause of SIDS is not known with certainty. It is possible that some cases of SIDS are the result of a combination of factors. Doctors have proposed several different theories for SIDS:

  • Bacterial infections. A British study published in May 2008 reported that some cases of SIDS appear to result from previously undetected bacterial infections.
  • Abnormalities in the part of the brain stem that controls breathing. A study published in the Journal of the American Medical Association in the fall of 2007 is one of the strongest pieces of evidence so far that innate differences in brain structure may put some babies at increased risk of SIDS.
  • Smothering caused by sleeping on the stomach. This theory holds that babies put to sleep lying on the stomach may breathe in their own exhaled carbon dioxide because they do not have the same ability as older children to move their heads during sleep to get more oxygen.
  • Episodes of apnea (sudden cessation of breathing). Babies sometimes stop breathing periodically for reasons that are still not understood.
  • Abnormalities in heart rhythm. About 10 percent of babies who die of SIDS have been found to have a gene associated with sudden episodes of extremely rapid heartbeat.
  • Triple-risk theory. This theory proposes to explain SIDS as the end result of three factors: a biological vulnerability (such as a weakened heart or abnormal brain stem), an environmental problem (such as sleeping on the stomach), and being too young to regulate breathing and other vital functions as effectively as older children.

Theories that are no longer accepted include the notion that SIDS is caused by vaccinations, by dust mites or other insects in the crib mattress,

or by toxic gases released by materials used in the manufacture of crib mattresses.

The symptoms of SIDS have already been described.


SIDS is a diagnosis of exclusion, which means that the doctor can list it as the cause of a baby's death only after all other possible causes have been ruled out. It is particularly important to exclude the possibility that the baby had been abused. The American Academy of Pediatrics has drawn up a list of criteria that must be met in order to distinguish SIDS from child abuse:

  • There has been a complete autopsy of the baby, and the autopsy findings are consistent with a diagnosis of SIDS.
  • There is no evidence of head trauma or significant disease.
  • There is no evidence of trauma to the baby's bones.
  • Other possible causes of death have been ruled out, including pneumonia, metabolic disorders, dehydration, severe birth defects, dehydration, massive infection, trauma to the abdomen, or carbon monoxide poisoning.
  • There is no evidence that the baby was given alcohol, drugs, or other toxic substances.
  • There is no evidence of foul play when the death scene is investigated.
  • The baby's medical history does not indicate previous health problems.


There is nothing that can be done to treat the infant when SIDS occurs. Treatment of the parents includes support and understanding. However, the doctor and other health professionals must at the same time conduct a thorough investigation into the circumstances surrounding the baby's death. There are some differences among the states as to the way in which the postmortem (after death) investigation is carried out, but all states require an investigation before the death can be defined as SIDS. It is difficult for many parents to accept the need for an autopsy and an evaluation of the bed and room in which the baby died when they are

grieving. However, ruling out the possibility of abuse or intentional suffocation of the child is a legal necessity.

Circumstances that concern doctors as well as law enforcement when a baby dies suddenly include:

  • The child was seven months of age or older. SIDS is unusual in this age group.
  • The pregnancy was unwanted.
  • There have been previous unexplained infant deaths in the family.
  • Family members have a history of arrests for violent behavior.


The CDC recommends the following precautions to reduce the risk of SIDS:

  • Infants should always be placed on their backs to sleep when they are left alone; they should be placed on their stomachs only when they are awake and supervised by someone responsible.
  • If the baby sleeps in a crib, the crib's mattress should be firm and fit snugly into the crib frame. Such other firm sleeping surfaces as bassinets or cradles are also fine.
  • The baby should be dressed in a sleeper or pajama to keep it warm rather than being covered by a blanket.
  • Parents who co-sleep with a baby should never smoke, drink alcohol, or use drugs when sleeping with the baby. It is better to have the baby sleep in a crib or bassinet next to the parents’ bed rather than sharing the bed.
  • Parents should never put a baby on a couch, waterbed, or pillow for a nap.
  • Parents should never smoke in the same room as the baby or allow anyone else to do so.
  • Caregivers should never place the baby to sleep or nap with any pillows, stuffed toys, bumper pads, comforters, quilts, or sheepskins.

The Future

Present research into SIDS is focused on obtaining a better understanding of the causes of the tragedy, and the factors that may increase

a child's risk of dying of SIDS. Some scientists are looking into possible genetic factors that may affect a child's risk of SIDS.

SEE ALSO Child abuse; Obesity; Prematurity; Shaken baby syndrome; Smoking


Autopsy: The examination of a body after death to determine the cause of death.

Brain stem: The lower part of the brain directly connected to the spinal cord. It controls breathing and other vital functions.

Co-sleeping: Allowing a baby to sleep in the same bed as its parents. It is also called bed sharing.

Postmortem: Referring to the period following death.

For more information


Horchler, Joani Nelson, and Robin Rice. SIDS and Infant Death Survival Guide: Information and Comfort for Grieving Family and Friends and Professionals Who Seek to Help Them, revised and updated. Cheverly, MD: SIDS Educational Services, 2003.


American Sudden Infant Death Syndrome Institute. Reducing the Risk of SIDS. Available online at http://sids.org/nprevent.htm (updated 2007; accessed July 9, 2008).

Centers for Disease Control and Prevention (CDC). Sudden Infant Death Syndrome: Home. Available online at http://www.cdc.gov/SIDS/index.htm (updated April 7, 2008; accessed July 9, 2008).

First Candle. When a Baby Has Died. Available online at http://www.firstcandle.org/whenababy/whenababy.html (accessed July 9, 2008). First Candle is a charity that offers support and counseling to families that have lost a baby. It has a toll-free bilingual crisis counseling hotline staffed twenty-four hours a day, seven days a week at (800) 221-7437.

Mayo Clinic. Sudden Infant Death Syndrome (SIDS). Available online at http://www.mayoclinic.com/health/sudden-infant-death-syndrome/DS00145 (updated June 13, 2007; accessed July 9, 2008).

National Institute of Child Health and Human Development (NICHD). SIDS: “Back to Sleep” Campaign. Available online at http://www.nichd.nih.gov/sids/sids.cfm (updated February 22, 2008; accessed July 9, 2008).