Sudden infant death syndrome (also known as SIDS) is defined as the sudden death of an infant younger than 1 year of age. If the child's death remains unexplained after a formal investigation into the circumstances of the death (including performance of a complete autopsy, examination of the death scene, and review of the clinical history), the death is then attributed to SIDS.


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 of age, is found dead in bed. In most cases, no sign of distress is identifiable. The baby typically feeds normally prior to being placed in bed tosleep. The infant is then discovered lifeless, without pulse or respiration. Cardiopulmonary resuscitation (CPR) may be initiated at the scene, but evidence shows a lack of beneficial effect from CPR. The cause of death remains unknown despite a careful review of the medical history, scene investigation, X-rays, and autopsy.
  1. SIDS is rare during the first month of life. Risk peaks in infants 2-4 months of age and then declines.
  2. About 90% of SIDS deaths occur in infants younger than 6 months of age.
  • Even though the specific cause (or causes) of SIDS remains unknown, scientific efforts have eliminated several previously held theories.
  • We now know the following about SIDS:
  1. Apnea (cessation of breathing) of prematurity and apnea of infancy are felt to be clinical conditions that are distinct from SIDS. Infants with apnea may be managed with electronic monitors prescribed by doctors that track heart rate and respiratory activity. Apnea monitors will not prevent SIDS.
  2. SIDS is not predictable or preventable.
  3. Infants may experience episodes termed apparent life-threatening events (ALTEs). These are clinical events in which young infants may experience abrupt changes in breathing, color, or muscle tone. Common causes of ALTEs include viral respiratory infection (RSV), gastroesophageal reflux disease, or seizure. However, no definite scientific evidence links ALTEs as events that may lead to SIDS.
  4. SIDS is not caused by immunizations or bad parenting.
  5. SIDS is not contagious or hereditary.
  6. SIDS is not anyone's fault.


The list of signs and symptoms mentioned in various sources for Sudden Infant Death Syndrome includes the 13 symptoms listed below:

  • Apnea.
  • Limpness.
  • Choking.
  • Gagging.
  • Cyanosis.
  • Hemorrhagic skin spots.
  • Pulmonary edema.
  • Dilated heart.
  • Red pharynx.
  • Minor inflammatory changes in airways.


Typically the infant is found dead after having been put to bed, and exhibits no signs of having suffered.


SIDS is a diagnosis of exclusion. It can only be applied to an infant whose death is sudden and unexpected, and remains unexplained after the performance of an adequate postmortem investigation.


The cause (or causes) of SIDS is still unknown. Despite the dramatic decrease in the incidence of SIDS in the United States in recent years, SIDS remains one of the leading causes of death during infancy beyond the first 30 days after birth. It is generally accepted that SIDS may be a reflection of multiple interacting factors.


  • Infant development: A leading hypothesis is that SIDS may reflect a delay in the development of nerve cells within the brain that are critical to normal heart and lung function. Research examinations of the brain stems of infants who died with a diagnosis of SIDS have revealed a developmental delay in formation and function of several serotonin-binding nerve pathways within the brain (serotonin is an example of a brain chemical known as a neurotransmitter that is important for brain function). These pathways are thought to be crucial to regulating breathing, heart rate, and blood pressure responses.
  1. The hypothesis is that certain infants, for reasons yet to be determined, may experience abnormal or delayed development of specific, critical areas of their brain. This could negatively affect the function and connectivity to regions regulating arousal.
  2. Arousal, in this context, refers to an infant's ability to awaken and/or respond to a variety of physiological stimuli. 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 may alter the levels of oxygen or carbon dioxide in the infant's blood. Normally, these changes would trigger arousal responses, prompting the infant to move his or her head to the side to alleviate this obstruction.
  3. In addition, other normally protective responses to stressful stimuli may be defective in infants who are vulnerable to SIDS. One such reflex is the laryngeal chemoreflex. This reflex results in changes in breathing, heart rate, and blood pressure when portions of the airway are stimulated by fluids like saliva or regurgitated stomach contents. Having saliva in the airway may activate this 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 laryngeal reflexes are also diminished in active sleep in the facedown position.
  • Rebreathing asphyxia: When a baby is facedown, air movement around the mouth may be impaired. This can cause the baby to re-breathe carbon dioxide that the baby has just exhaled. Soft bedding and gas-trapping objects, such as blankets, comforters, water beds, and soft mattresses, are other types of sleep surfaces that may impair normal air movement around the baby's mouth and nose when positioned facedown.
  • 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 objects obstructing the airway.


Most deaths due to SIDS occur between 2 and 4 months of age, and incidence increases during cold weather. African-American infants are twice as likely and Native American infants are about three times more likely to die of SIDS than caucasian infants. More boys than girls fall victim to SIDS.


Other potential risk factors include:


  • smoking, drinking, or drug use during pregnancy;
  • poor prenatal care;
  • prematurity or low birth-weight;
  • mothers younger than 20;
  • tobacco smoke exposure following birth;
  • overheating from excessive sleepwear and bedding;
  • stomach sleeping.


There is no home care for SIDS. Call 911 for emergency medical services. However, if any of the parents, caregivers, or bystanders has been instructed in infant CPR (cardiopulmonary resuscitation), they should perform CPR prior to paramedic arrival.


Medical responses


The initial response is directed by the emergency personnel at the scene according to pediatric advanced life support protocols. Resuscitation measures may be implemented unless signs of death are obvious.


Initial responses may include the following:


  • Assessment of the infant's airway, breathing, pulse, and blood sugar level.
  • Placement of a tube into the trachea to maximize oxygen delivery.
  • Emergency responders may establish IV access; medications to restore heartbeat may be given according to advanced life-support protocols.
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