Sudden Infant Death Syndrome Clinical Presentation

Updated: May 16, 2022
  • Author: Lynn Barkley Burnett, MD, EdD, JD; Chief Editor: Kirsten A Bechtel, MD  more...
  • Print


The classic presentation of sudden infant death syndrome (SIDS) begins with an infant who is put to bed, typically after breastfeeding or bottle-feeding. Checks of the baby at varying intervals are unremarkable, but the baby is found dead, usually in the position in which he or she had been placed at bedtime or naptime. Although most of infants are apparently healthy, many parents state that their babies “were not themselves” in the hours before death. Diarrhea, vomiting, and listlessness have been reported in the 2 weeks before death.

The observations most commonly reported with Brief Resolved Unexplained Events (BRUEs: formerly Apparent Life-Threatening Events)  are as follows:

  • Cyanosis (50-60%)

  • Breathing difficulties (50%)

  • Abnormal limb movements (35%)

Antecedent events may provide an indication regarding the etiology, particularly the relation of the BRUE to feeding or descriptions suggestive of seizure.

After efforts have been made to calm the parents, it is important to determine the exact time sequence before and during the event by taking a detailed history. The following questions should be asked:

  • Did the infant have a foreign body, trauma, or ingestion?

  • Does the infant have a history of apnea?

  • What activity did the infant exhibit before the BRUE? Apnea following paroxysmal cough, in an infant with upper respiratory infection, suggests pertussis; arching with apnea after feeding—with or without milk or formula in the oronasal passages—suggests gastroesophageal reflux (GER)

  • What was the time and amount of the last meal? Parents may misinterpret postprandial regurgitation as a life-threatening event

  • Was the baby asleep or awake? GER may occur in an awake infant after feeding

  • What was the child’s position?

  • What was observed first? Chest wall movement and effort in respiration, in the absence of airflow, indicates obstructive apnea, whereas the absence of chest wall movement, respiratory effort, and airflow is consistent with central apnea

  • What was the period of apnea (in seconds)? Most healthy babies momentarily stop breathing when they are asleep

  • Did the infant change color? If the patient turned blue, ask "how blue?", inquire as to lighting in the room, and ascertain the location of the cyanosis; some healthy babies appear to turn blue around the mouth when crying, and acrocyanosis or color change during defecation may be misinterpreted as a life-threatening event

  • What was the baby’s tone (eg, limp, stiff, or shaking)? Stiffening or clonic movement followed by apnea suggests postictal apnea

  • What was the duration of the event?

  • What was done (eg, cardiopulmonary resuscitation [CPR]), and how was it done? Carefully question parents or other witnesses about their efforts to revive the baby; the absence of a need for resuscitative effort is consistent with a benign cause, whereas the need for respiratory resuscitation or CPR suggests a more serious cause

Children are poorly served if abuse is not considered in the differential diagnosis of infants with BRUEs. Autopsy cannot distinguish death due to SIDS from death by suffocation. However, certain elements of the history may raise a suspicion of abuse, though none of these elements is pathognomonic.

Circumstances surrounding death

Findings consistent with SIDS are as follows:

  • Apparently healthy infant who is fed, put to bed, and found lifeless

  • Silent death

  • Emergency medical services (EMS) resuscitation unsuccessful

  • Age at death younger than 7 months (90% of cases; peak incidence, 2-4 months)

Findings that raise the suspicion of child abuse are as follows:

  • History that is atypical for SIDS, discrepant, or unclear

  • Prolonged interval between bedtime and death

  • Age at death 6 months or older

Course of pregnancy, delivery, and infancy

Findings consistent with SIDS are as follows:

  • Prenatal care ranging from minimal to maximal

  • A history of cigarette use during pregnancy, as well as premature delivery or low birth weight is reported.

  • Subtle defects in feeding, crying, and neurologic status (eg, hypotonia, lethargy, and irritability) may have been present. Other factors include

  • Diminished postneonatal height and weight gain

  • Twins or triplets

  • Thrush, pneumonia, spitting, GER, tachypnea, tachycardia, and cyanosis

  • Greater likelihood of previous hospital admission

Findings that raise the suspicion of child abuse are as follows:

  • Unwanted pregnancy

  • Little or no prenatal care

  • Late arrival for delivery or birth outside a hospital

  • No well-baby care or few visits; no immunizations

  • Use of alcohol or other drugs during and after pregnancy

  • Infant described as hard to care for or discipline

  • Deviant feeding practices

  • Previous unexplained medical disorders (eg, seizures)

  • Previous episodes of apnea in the presence of the same person

Previous infant deaths in family

The following is consistent with SIDS:

  • First, unexplained, and unexpected infant death

Findings that raise the suspicion of child abuse are as follows:

  • Reese – More than 1 previous unexplained or unexpected infant death

  • Committee on Child Abuse and Neglect – Previous unexpected or unexplained death(s) of 1 or more siblings while under the care of the same unrelated person

Previous involvement of law enforcement or child protective services

Child abuse should be considered in cases where 1 or more family members have been arrested for violent behavior 2 or more times.


Physical Examination

Care should be taken at the scene of death to examine for signs of obstruction of the external airways, accidental entrapment of the head, or other environmental factors (eg, ambient temperature or a source of heating for carbon monoxide exposures) that may have contributed to the death.

Clinical assessment after brief resolved unexplained events

After a BRUE, many patients present to the emergency department (ED) in no acute distress. In 50% of these infants, physical examination is entirely normal. Pyrexia is documented in 25% of patients presenting to the ED; infection is noted in 25%.

The literature has varying recommendations concerning the extensiveness of the ED workup of an apparently healthy infant who presents following a BRUE. Agreement does exist regarding elicitation of a detailed history and performance of a thorough physical examination. Findings from the history and physical examination should enable the physician to determine if the child had a BRUE and whether the apneic episode was central, obstructive, or mixed.

Examine the patient after all clothing has been removed. Direct the physical examination toward identifying congenital anomalies of the heart or central nervous system (CNS) and recognizing dysmorphic features indicative of a congenital syndrome. Findings of poor muscle tone or irregular respirations indicate a true BRUE.

Truncal bruising and other lesions

Most accidental bruising occurs over bony prominences. Contusions in “soft” sites (eg, cheeks or trunk) suggest abuse. An examination of babies with accidental bruises revealed no infant with a contusion measuring more than 10 mm in any diameter; some infants did have more than 1 contusion.

Development of a contusion is determined by a number of factors, including degree of blunt force applied to the skin, tissue density, tissue vascularity, fragility of blood vessels, and amount of blood escaping into surrounding tissues.

On a given person, bruises of identical age and cause may not appear as the same color and may not change at the same rate. Red, blue, purple, or black bruises may occur at any time between 1 hour after the causal trauma and resolution of the contusion. The presence of red coloration therefore has no bearing on the age of the bruise. A bruise with any yellow must be older than 18 hours. Aside from describing bruises that are yellow, brown, or green as older, it is difficult to specify age any further.

The following may be observed:

  • Pinch or human bite marks

  • Wounds in different stages of healing

  • Scalds or burns, including those caused by cigarettes

  • Fractures, particularly if of different ages

  • Pupillary changes

Retinal hemorrhages, though strongly associated with inflicted head injury (shaken impact syndrome), are not specific for that diagnosis. They may be seen in accidental trauma, subarachnoid hemorrhage, sepsis, coagulopathy, severe hypertension, and galactosemia (albeit rarely), as well as after resuscitation, in conjunction with papilledema, and in as many as 40% of vaginally delivered newborns, with resolution taking up to 1 month after birth.

Southall et al noted frank bleeding from the nose or mouth in 11 of 38 suspected child abuse cases but in none of the 46 control subjects (children with recurrent BRUE attributable to a natural medical cause). [84]

Contribution of clinical examination to death investigation

In the case of a deceased infant, the National Association of Medical Examiners makes it very clear that “medical examiners and coroners have the sole legal authority to investigate deaths that are sudden, unexpected, unexplained, and potentially due to external causes such as injury” and that “examination or manipulation of the deceased body by child maltreatment experts without proper statutory authority or family permission may constitute a tort or be a violation of criminal law.”

If an infant arrives in cardiopulmonary arrest, relevant findings from a clinical examination conducted during the course of a resuscitation attempt should be carefully documented in the chart. Such findings will complement the autopsy and other components of the death investigation. The clinical examination should address many of the same elements indicated for assessment of a BRUE, modified as appropriate for the unresponsive patient.

Autopsy findings

At autopsy, the infant usually exhibits signs of normal hydration and nutrition, which is evidence of proper care. No signs of obvious or occult trauma should be present. Gross examination of the organs generally reveals no evidence of a congenital abnormality or acquired disease process consistent with a recognizable cause of death.

Intrathoracic petechiae are typically present on the surfaces of the thymus, pleura, and epicardium. [111] The frequency and severity of petechiae have been noted to be similar regardless of whether infants were discovered face down on the sleep surface, face up, or face to the side. This finding suggests that centrally mediated airway failure, such as that seen with apnea or failed gasping rather than external airway obstruction, is likely in SIDS. [112]

Microscopic examination may reveal minor inflammatory changes within the tracheobronchial tree or signs of passive congestion of the organs. Very mild myocardial lymphocyte and macrophage infiltration with scattered necrotic cardiomyocytes may be seen in SIDS; this is not considered to be pathologic. [113] Histologically, the thymus and adrenal glands are normal.

SIDS versus infanticide

In addition to the abnormalities described (see above), several physical findings may help distinguish SIDS from suspected infanticide. Findings consistent with SIDS include the following:

  • Serosanguineous watery, frothy, or mucoid discharge from mouth or nose

  • Reddish-blue mottling from postmortem lividity on the face and dependent portions of the body

  • Marks on pressure points of the body

  • Well-cared-for appearance, with no significant skin trauma

Findings that raise the suspicion of child abuse include the following:

  • Malnutrition or neglect

  • Cutaneous injuries, traumatic lesions, or abnormalities of the head or body (eg, of the conjunctiva, fundi, scalp, oral cavity, ears, neck, trunk, anogenital region, or extremities, including fractures)

  • Distribution of hypostasis indicating that the child was in a different position from that stated

  • Pressure ischemia over the nose and mouth

Absence of physical stigmata does not prove that the death was natural. So-called gentle battering occurs when a physical act leaves no mark, as when a hand or pillow is placed over the face or when the infant is placed face down on a pillow or soft mattress, occasionally without any criminal intent (eg, to stifle a cry). Physical examination of SIDS infants may reveal evidence of terminal motor activity (eg, clenched fists).

It is important not to misinterpret postmortem changes or physical findings often seen in SIDS-related deaths (eg, by confusing postmortem lividity or anal dilatation with trauma secondary to abuse).