Sudden Infant Death Syndrome
Sudden Infant Death Syndrome (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, and review of the symptoms or illnesses
the infant had prior to dying and any other pertinent medical history.
SIDS is the leading cause of death in infants between 1 month and
1 year of age. African American children are two to three times
more likely than white babies to die of SIDS, and Native American
babies are about three times more susceptible. Also, more boys are
SIDS victims than girls.
What Are the Risk Factors for SIDS?
A number of factors seem to put a baby at higher risk of dying of
SIDS. Babies who sleep on their stomachs are more likely to die
of SIDS than those who sleep on their backs. 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. Other
risk factors include mothers who are less than 20 years old at the
time of their first pregnancy, babies of mothers who had no or late
prenatal care, and premature or low birth weight babies.
What Causes SIDS?
Mounting evidence suggests that 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 controlling 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. Cigarette
smoking during pregnancy, for example, can reduce the amount of
oxygen the fetus receives.
Scientists believe that the abnormalities that are present at birth
may not be sufficient to cause death. Other possibly important events
occur after birth such as lack of oxygen, excessive carbon dioxide
intake, overheating or an infection. For example, many babies experience
a lack of oxygen and excessive carbon dioxide levels when they have
respiratory infections that hamper breathing, or they rebreathe
exhaled air trapped in underlying bedding when they sleep on their
stomachs. Normally, infants sense such inadequate air intake, and
the brain triggers the babies to wake from sleep and cry, and changes
their heartbeat or breathing patterns to compensate for the insufficient
oxygen and excess carbon dioxide. A baby with a flawed arcuate nucleus,
however, might lack this protective mechanism and succumb to SIDS.
Such a scenario might explain why babies who sleep on their stomachs
are more susceptible to SIDS, and why a disproportionately large
number of SIDS babies have been reported to have respiratory infections
prior to their deaths. Infections as a trigger for sudden infant
death may explain why more SIDS cases occur during the colder months
of the year, when respiratory and intestinal infections are more
The numbers of cells and proteins generated 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 alter 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 acylCoA dehydrogenase deficiency,
which prevents the 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, 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
Prepared by National Institute of Child Health and Human Development
Public Information and Communications Branch
How Many Babies Die From SIDS?
According to the Center for Health Statistics (NCHS), each year
from 1983 to 1991, the number of SIDS deaths reported in the United
States ranged from 5,000 to 6,000. In April of 1992, the American
Academy of Pediatrics announced that healthy infants should sleep
on their back to reduce the risk of SIDS. Beginning that year, SIDS
deaths began to decline somewhat, to 4,890. In June of 1994, the
Back to Sleep campaign began, and SIDS deaths declined even more.
This decline continued throughout the 1990s, and, according to the
NCHS, final figures for SIDS deaths in 1999 were approximately half
of what they were in 1991 (2,648 versus 5,349).
When considering the overall number of live births each year in
the United States, SIDS remains the leading cause of death in infants
between 1 month and 1 year of age, and the third leading cause of
death in infants birth to 1 year of age, behind congenital abnormalities
and short gestation/low birth weight.
(National Vital Statistics Report, June 26, 2001)
How Do Professionals Diagnose SIDS?
Often the cause of an infant death can be determined only through
a process of collecting information, conducting sometimes complex
forensic tests and procedures, and talking with parents and physicians.
When a death is sudden and unexplained, investigators, including
medical examiners and coroners, use the special expertise of forensic
medicine (application of medical knowledge to legal issues). SIDS
is no exception.
Health professionals make use of three avenues of investigation
in determining a SIDS death: the autopsy; death scene investigation;
and review of victim and family case history.
The autopsy provides anatomical evidence through microscopic examination
of tissue samples and vital organs. An autopsy is important because
SIDS is a diagnosis of exclusion. A definitive diagnosis cannot
be made without a thorough postmortem examination that fails to
point to any other possible cause of death. Also, if a cause of
SIDS is ever to be uncovered, scientists will most likely detect
that cause through evidence gathered from a thorough pathological
A Thorough Death Scene Investigation
A thorough death scene investigation involves interviewing the parents,
other caregivers, and family members; collecting items from the
death scene; and evaluating that information. Although painful for
the family, a detailed scene investigation may shed light on the
cause, sometimes revealing a recognizable and possibly preventable
cause of death.
Review of the Victim and Family Case History
A comprehensive history of the infant and family is especially critical
to determine a SIDS death. Often, a careful review of documented
and anecdotal information about the victim's or family's history
of previous illnesses, accidents, or behaviors may further corroborate
what is detected in the autopsy or death scene investigation.
Investigators should be sensitive and understand that the family
may view this process as an intrusion, even a violation of their
grief. It should be noted that, although stressful, a careful investigation
that reveals no preventable cause of death may actually be a means
of giving solace to a grieving family.
What SIDS Is and What SIDS Is Not
SIDS Is: The major cause of death in infants from 1 month to 1 year of
age, with most deaths occurring between 2 and 4 months
Sudden and silent - the infant was seemingly healthy
Currently, unpredictable and unpreventable
Determined only after an autopsy, an examination of the death
scene, and a review of the clinical history
Designated as a diagnosis of exclusion
A recognized medical disorder listed in the International Classification
of Diseases, ( 9th Revision)
An infant death that leaves unanswered questions, causing intense
grief for parents and families.
SIDS Is Not: Caused by vomiting and choking, or minor illnesses such as colds
Caused by immunizations
The cause of every unexpected infant death
* SIDS is not caused by a lack of love.
* SIDS is not caused by suffocation, vomiting or choking.
* SIDS is not caused by baby shots.
* SIDS is not caused by child abuse.
National SIDS Resource Center (What is SIDS?)
New Learning, New Policy -- How to Reduce the Risk
Before leaving the hospital with your brand-new baby, you'll
be given a long list of instructions. Among them is this: Always
place your baby on her back to sleep.
Researchers began putting out this advice in 1992; it was reinforced
again four years later when the American Academy of Pediatrics
recommended that all healthy babies be put to sleep on their back.
In 1994, a national "Back to Sleep" campaign was launched
to promote the supine - or back-sleeping - position during sleep.
Surveys have confirmed that more and more people are putting their
little ones to sleep on their back, which has reduced the incidence
of SIDS about 43 percent.
New parents have so much they're trying to learn. While most
of the training comes on the job, you can take certain steps ahead
of time to keep your baby safe, ease into your new role, and lessen
any fears you may have about childrearing. When it comes to sleep
and reducing the risk of SIDS, be sure to follow the guidelines
Safe Sleep Checklist Here are some
smart strategies to minimize the risk of SIDS. Print out this
checklist and post it by your baby's bed.
- Prenatal regimen: Be sure you get early and regular prenatal
care, including frequent doctor visits and good nutrition, and
don't use drugs or alcohol.
- Bedding: Use a firm mattress in the crib or bassinet so your
baby doesn't sink in. Do not put fluffy blankets, thick quilts,
comforters, or a sheepskin under or over the baby, and remove
any soft stuffed toys or pillows from the crib.
- Positioning: Always put your baby to sleep on her back. To
keep a newborn on her back, swaddle her in a blanket with her
hands placed up by her mouth so she can comfort herself. Or,
you can use a "Halo Sleep Sack," a wearable blanket
that helps baby sleep comfortably on his or her back. "Halo
Sleep Sacks" can be purchased from SIDSMA
and from various retailers.
- Temperature: Avoid too much heat in your baby's room. Keep
the temperature at a level that feels comfortable to you, and
don't overdress your baby at nighttime.
- Well-baby checkups: Take your baby to the doctor for routine
checkups and scheduled immunizations.
- Clean air: Never smoke around your baby or allow anyone to
smoke around your baby. Encourage the Smoke-free
- Breastfeeding: Breastfeed your baby, if possible, to get
her off to a strong, healthy start.
- Tummy Time (always supervised): Encourage your baby to spend
time on her tummy when she is awake to strengthen her arms and
shoulder muscles. Put her on the floor on her blanket, or in
a play pen with toys that spark her interest.