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Sudden infant death syndrome (also known as SIDS) is defined as the sudden death of an infant younger than 1 year. Even after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history, the child's death remains unexplained. Sudden infant death is a tragic event for any parent or caregiver.
SIDS is suspected when a previously healthy infant, usually younger than 6 months, is found dead in bed. In most cases, no sign of distress is identifiable. The baby feeds normally prior to being placed in bed to sleep. Then the baby is found in the same position in which he or she was placed at bedtime. Cardiopulmonary resuscitation (CPR) may be initiated at the scene and en route to the hospital, but evidence shows lack of beneficial effect, and the child is later declared dead at the hospital. The cause of death remains unsolved despite a careful review of the medical history, scene investigation, x-rays, and autopsy.
SIDS is rare during the first month of life. Risk peaks in infants aged 2-4 months, and then declines.
About 90% of SIDS deaths occur in infants younger than 6 months.
Even though the cause of SIDS remains unknown, scientific efforts have eliminated various misleading theories. We know that SIDS is NOT any of these conditions:
Apnea (not breathing): Infants with apnea can be resuscitated. A crib monitor can detect when a SIDS victim stops breathing, but a SIDS victim is already dead when that happens.
SIDS is not predictable or preventable.
A near-SIDS event is also known as an apparent life-threatening event (ALTE). However, there is no definite supportive evidence to classify this condition as an event that might lead to SIDS.
SIDS is not caused by immunizations or bad parenting.
SIDS is not contagious or hereditary.
SIDS is not anyone's fault.
SIDS Causes
The cause or causes of SIDS are still unknown. Despite the dramatic decrease in the incidence of SIDS in the United States in recent years, SIDS remains the number one cause of death during infancy beyond the first 30 days after birth. It is generally accepted that SIDS may be a reflection of a variety of causes of death.
Infant development: A leading hypothesis for a large proportion of SIDS cases is that SIDS may reflect a delayed development in heart and lung function. Examinations of the brainstems of infants who died with a diagnosis of SIDS have revealed a developmental delay of the arcuate nucleus—a region of the brain thought to be involved with respiratory and blood pressure responses.
The hypothesis is that certain infants, for reasons yet to be determined, may have a maldevelopment or delay in maturation of certain areas of their brain. This could negatively affect the function and connectivity to regions regulating arousal.
Arousal, in this context, refers to an infant's ability to awaken or move himself when faced with a life-threatening decrease in oxygen. For example, a child sleeping facedown may move his or her face into such a position so that the nose and mouth are completely obstructed. This decreases the oxygen in the infant's blood. Normally, this triggers arousal mechanisms that arouse the infant to move his or her head to the side to prevent this obstruction.
In addition, protective responses to other life-threatening stimuli have been compared in children placed facedown versus face-up when put to sleep. One life-threatening reflex is the laryngeal chemoreflex, a reflex that leads breathing and heartbeat to stop. Having saliva in the airway may activate this dangerous reflex, and swallowing may be important to keep the airway clear. When an infant is in the facedown position, the rate of swallowing is decreased. Protective arousal responses to these dangerous laryngeal reflexes are also diminished in active sleep in the facedown position.
The facedown position may also be implicated in triggering a dive reflex. In experiments, young monkeys that receive a cold or wet stimulus to the face stop breathing. This situation may be compared to a young infant sleeping facedown on a wet sheet from a regurgitated feeding.
Rebreathing asphyxia: Diminished oxygen supply may be associated with the facedown position. When a baby is facedown, air movement around the mouth is not very good. This can cause the baby to rebreathe carbon dioxide that the baby has just exhaled. Increased carbon dioxide may decrease the ability of the infant to arouse when there is some obstruction of the mouth preventing normal breathing. Soft bedding and gas-trapping objects, such as blankets, waterbeds, and soft mattresses, are other sources of poor air movement around the baby's face.
Hyperthermia (increased temperature): Overdressing, using excessive coverings, or increasing the air temperature may lead to an increased metabolic rate in these infants and eventual loss of breathing control. However, it is unclear whether the increased temperature is an independent factor or if it is just a reflection of the use of more clothing or blankets that may act as potentially oxygen-trapping objects.
SIDS Symptoms
Sudden infant death remains an unpredictable, unpreventable, and inexplicable tragedy. The baby is seemingly healthy without any sign of distress prior to the incident. It is a syndrome of which the first symptom is death.
Death occurs while the infant is sleeping and occurs rapidly.
Typically, it is a silent event. The baby does not cry.
The infant usually appears to be well developed and well nourished. These babies generally appear healthy or may have had a minor upper respiratory or gastrointestinal infection in the last 2 weeks of life.
Exams and Tests
SIDS is a diagnosis of exclusion. The cause of an infant's death can be determined only through a process of collecting information and conducting sometimes-complex forensic tests and procedures. All other causes of death should be investigated prior to making the diagnosis of SIDS.
Four major avenues of investigation aid in the determination of a SIDS death: postmortem lab tests, autopsy, death scene investigation, and the review of victim and family case history.
Postmortem laboratory tests are done to rule out other causes of death (for example, electrolytes are checked to rule out dehydration and electrolyte imbalance). In SIDS, laboratory tests are not consistently abnormal.
An autopsy provides clues as to the cause of death. The autopsy findings in SIDS victims are very subtle and yield only supportive, rather than conclusive, findings to explain SIDS.
Two most common autopsy findings are an increased number of star-shaped cells in the brainstem, referred to as brainstem gliosis, and the occurrence of tiny red or purple spots (tiny hemorrhages) on the surface of the heart, in the lungs, and thymus.
Chronic asphyxia—long-standing decreased oxygen delivery to internal organs—has been demonstrated in nearly two-thirds of SIDS victims. Swelling of the lungs and tiny purple spots are observed. Certain brain stem abnormalities can be found.
A thorough investigation of the death scene consists of interviewing the parents, other caregivers, and family members; collecting items from the death scene; and evaluating that information. A detailed scene investigation may reveal a recognizable and possibly preventable cause of death.
A parent or caregiver is asked these questions:
Where was the baby?
What was the baby doing?
Was the baby alone?
How was the baby sleeping?
You should let your doctor know about any family or infant medical history. Any suspicious findings may further corroborate what is detected in the autopsy or death scene investigation.
SIDS Treatment
Self-Care at Home
There is no home care for SIDS. Call 911 for emergency medical services. However, if any of the parents or caregivers have been instructed in infant CPR , they should perform CPR prior to paramedic arrival.
Medical Treatment
The initial treatment is initiated by the paramedics at the scene according to neonatal and pediatric advanced life support. Resuscitation measures are implemented unless there is evidence of prolonged death, such as stiffness and skin color that would indicate the infant has been dead for some time.
Upon hospital arrival, the emergency doctor assesses the infant's airway, breathing, pulse, and blood sugar level.
In order to maximize the oxygen delivery to the brain, a tube may be placed in the trachea.
The doctor then establishes IV access, and medications to restore heartbeat are given according to advanced life support protocols.
A complete laboratory workup is performed to exclude any other potential causes of death, such as infections, metabolic disturbances, or poisoning.
The doctor may have x-rays taken. They may contribute in determining the cause of death.
Next Steps
Prevention
There is currently no way to predict which newborns will die of SIDS. SIDS has been linked to certain risk factors. Therefore, eliminating or preventing these factors has diminished the frequency of SIDS.
Sleeping position and conditions: Educate baby-sitters, day care providers, grandparents, and everyone who cares for your baby about SIDS risk. Try to forget the "what if" questions and concentrate on enjoying your child.
"Back to sleep": You should place your baby on his or her back or on a side to sleep at night and nap time. Babies positioned on their sides should be placed with their lower arm forward to help prevent them from rolling onto their stomachs.
You should avoid fluffy, loose bedding in your baby's sleep area.
Keep your baby's face clear of coverings.
Be careful not to overheat your baby by overdressing or adding unnecessary covers.
Don't allow anyone to smoke around your baby.
Use a firm mattress in a safety-approved crib.
Do not allow your baby to sleep alongside another person. The risk of unintentional smothering is too great.
Keep all "well-child" appointments, including immunizations.
Home monitoring: The use of home monitoring for infants perceived to be at risk of SIDS is still controversial. SIDS monitors are available that sound an alarm if the baby's breathing or heartbeat stops. The transthoracic electrical impedance monitors are by far the most frequently used and have the widest availability in the United States. This SIDS monitor detects the respiration and heart activity by using 3 electrodes. In case of breathing irregularities or decreased heart activity, the device gives an acoustic or optical alarm. The choice of SIDS monitor may integrate heart rate, respiratory rate, and pulse oximetry (blood oxygen saturation), or any combination of these 3 parameters. The information recorded should be downloaded periodically and examined by a doctor.
Current studies still echo the National Institutes of Health Consensus Report on SIDS. To date, no reports scientifically demonstrate the effectiveness of home monitoring for siblings of SIDS victims (babies born after a family has had a child die of SIDS).
Currently, certain guidelines exist for use of home cardiorespiratory monitoring:
Infants with one or more life-threatening episodes in which the baby turned blue or became limp requiring mouth-to-mouth resuscitation or vigorous stimulation
Symptomatic preterm infants
Siblings of 2 or more SIDS victims
Infants with certain diseases or conditions such as central breathing irregularities
Motor development: One recent study has focused on the relationship between sleeping position and an infant's motor development. Babies younger than 1 year who slept on their backs showed decreased upper trunk strength as reflected by their ability to crawl, sit tripod, or pull to stand.
This upper trunk development occurs routinely in infants who spend time in the facedown position. However, it is important to emphasize that face-up sleepers still attained these milestones within the accepted time range for normal. No significant difference was seen in age when either infant group started to walk.
Parents should incorporate a certain amount of tummy time while the infant is awake and observed. This type of play while baby is on his or her tummy is recommended for developmental reasons and to help prevent flat spots on the back of the head.
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