CHAPTER 72

Sudden Unexpected Infant Death and Brief Resolved Unexplained Events

Sarah M. Gustafson, MD, FAAP, and Lynne M. Smith, MD, FAAP

Sudden unexpected infant death (SUID) refers to all sudden, unexpected death in infants younger than 1 year. Sudden infant death syndrome (SIDS), a subcategory of SUID, is a diagnosis of exclusion following the death of a previously healthy infant younger than 1 year in which no contributing factors are identified (including the absence of an unsafe sleep environment) after obtaining a comprehensive medical history of the infant and family and performing a thorough postmortem examination and death scene investigation. In the United States, SUID is the most common cause of death in children younger than 1 year (excluding the neonatal period); in most cases, a contributory factor is present, such as an unsafe sleep environment.

A brief resolved unexplained event (BRUE) is a sudden, brief, and resolved event that occurs in an infant younger than 1 year of age and that involves at least 1 of the following findings: cyanosis or pallor; decreased, absent, or irregular breathing; change in tone; or decreased responsiveness. What is now known as BRUE was formerly termed an “apparent life-threatening event” (ALTE). For historical reasons, BRUE and SUID are discussed in this chapter because ALTE and SIDS were once thought to be related. A BRUE is not a risk factor for SUID, however.

Sudden Unexpected Infant Death

Epidemiology and Risk Factors

Sudden unexpected infant death accounts for 3,000 to 4,000 infant deaths per year in the United States, with an overall incidence of 0.93 per 1,000 live births. These figures were dramatically higher before the Safe to Sleep campaign (originally the Back to Sleep campaign) promoted by the American Academy of Pediatrics (AAP) to place babies in the supine position for sleep. Before the institution of this campaign, the annual death rate from what was then termed SIDS was approximately 5,000 to 8,000, with an incidence of approximately 1.4 per 1,000 live births.

Sudden unexpected infant death more commonly affects boys than girls and occurs more often in the winter months. The peak incidence of SUID occurs at 2 to 3 months of age, with 90% of deaths occurring before age 6 months.

The frequency of SUID differs in different populations in the United States and other countries. Although the incidence of SUID is decreasing among all groups, the rates in black and American Indian/Alaska Native children is 2 to 3 times the national average. One factor contributing to the higher rate of SUID is the increased incidence of nonsupine sleeping in black infants. In 2001, the prevalence of prone positioning was 11% for white infants and 15% to 21% for black infants.

Clinical Presentation

Patients with SUID present in cardiopulmonary arrest, with a history of previous good health or antecedent upper respiratory infection. They often present in the early morning hours, having succumbed during sleep. The physician cannot determine the cause of death of the deceased infant; that is the role of the coroner.

Pathophysiology and Risk Factors

Numerous epidemiologic, maternal, and infant factors have been associated with SUID, including preterm birth and intrauterine growth restriction (Box 72.1). Mothers of children with SUID are frequently young and unmarried, smoke cigarettes, and have had fewer than recommended doctor visits during the prenatal and postpartum periods. Parental alcohol use is also a risk factor for SUID. In 1 study SUID rates were 33% higher on New Year’s Day than any other day, which suggests that parents under the influence of alcohol are less able to monitor their infants safely. Despite initial reports and significant research efforts, no data have established a causal relationship of BRUEs, apnea, immunizations, or repeated episodes of cyanosis with SUID.

Although bedsharing was once promoted to enhance breastfeeding, accidental suffocation and SUID are associated with this practice. The importance of a safe sleep environment is underscored by a study published in 2000 in which the authors investigated 119 SUID cases over a 4-year period following the initiation of the Back to Sleep campaign. In only 8.4% of these SUID cases was the infant found in a nonprone position, alone in their bed and without any potential obstructions of the external airway by bedding.

Pediatricians play a critical role in counselling parents about safe sleep practices. One study reported that 11% of new mothers reported “usually” bedsharing, yet only 36% of parents had a conversation about bedsharing with their pediatrician. If their pediatrician had a negative view of bedsharing, parents were less likely to bedshare. If the pediatrician had a neutral view, parents were more likely to bedshare. Because approximately 20% of SUID cases in the United States occur while in the care of someone other than the parent, secondary caregivers and staff at child care centers also should be educated about the critical need for babies to sleep on their backs and in a sleep space free of blankets, pillows, and other objects that may obstruct an infant’s airway.

In addition to exposure to the environmental factors that increase an infant’s risk for SUID, most theories suggest the existence of an underlying vulnerability in those who experience SUID. The brain-stems of infants who died of SUID have significantly lower concentrations of serotonin and tryptophan hydroxylase, a biosynthetic enzyme of serotonin; higher serotonergic neuron counts; decreased serotonin 1A receptor binding; and reduced serotonin transporter binding in the medulla. Furthermore, several studies have shown a significant increase in monoamine oxidase A (MAO-A) gene polymorphisms that could cause overexpression of MAO-A. These findings suggest that abnormalities in serotonin synthesis, release, and clearance impair the infant’s ability to appropriately regulate arousal and respiratory drive in response to potential life-threatening challenges during sleep.

Numerous other associations with SUID have been reported, including altered polymorphisms of proinflammatory cytokines, abnormalities in other neurotransmitters, small mandibular size, disorders of fatty acid oxidation, and cardiac channelopathies, including long QT syndrome. The AAP does not currently recommend universal electrocardiography (ECG) screening at birth to identify potential SUID patients, however, although ECG has been recommended for infants with abnormal hearing screening because of the association of hearing deficits with long QT syndrome. Additionally, pulse oximetry in the newborn period may help identify infants with occult congenital heart disease.

The association between SUID and fatal child abuse has also received attention, although infanticide is estimated to be the cause in less than 5% of suspected SUID cases. The evaluation of the home environment of infants who have died from SUID, referred to as death scene investigations, may reveal factors that contributed to the death of some of these infants. Unsafe sleeping environments (eg, sofas) and parental drug paraphernalia may identify such factors. A complete postmortem examination may reveal prior or recent trauma. An autopsy should include an assessment for long bone fractures as well as intracranial hemorrhage, although these findings may account only for the existence of prior trauma rather than for the infant’s death. In some municipalities, child fatality boards review each case of reputed SUID to assess whether an etiology can be determined. Infants who are targets of medical child abuse may present with SUID or BRUE. Such infants are suffocated by the parents until they become apneic or die. Because distinguishing between SUID and intentional suffocation is quite difficult pathologically, the AAP Committee on Child Abuse and Neglect has cited factors that should heighten the physician’s suspicion for possible child abuse (Box 72.2). The use of in-hospital covert video surveillance has facilitated the recognition of apnea secondary to medical child abuse.

Management

In most jurisdictions, cases of SUID must be reported to the coroner’s office. The AAP recommends a prompt death scene investigation; appropriate use of available medical specialists by medical examiners and coroners, including pediatricians; and a postmortem examination within 24 hours of death, including radiologic skeletal surveys and toxicology and metabolic screening. A complete review of the medical records of the patient is essential. A timely information session with parents is recommended when the results of the investigation determine SUID or another cause of death.

Physicians must provide care to families whose infant has succumbed to SUID. Parents should be guided through issues such as planning the funeral and ending lactation when appropriate. For ongoing support, parents should be referred to groups and agencies to help them cope with the unexpected loss of their child. Information about these organizations can be obtained from First Candle (1-800-221-7437; www.firstcandle.org).

Prevention

Prevention of SUID has become a focus of public health measures, including promotion of smoking cessation and access to prenatal care. Parents must be instructed to avoid soft bedding for their infant, bedsharing, placing their infant on a sofa for sleep, and overheating, and they should be instructed to place their infant in the supine position in a crib. See Box 72.3 for additional recommendations.

Pacifier use has been associated with a decreased incidence of SUID. The AAP recommends that caregivers consider offering a pacifier at naptime and bedtime through age 12 months. The pacifier should not be reinserted after the infant falls asleep or coated in any sweet solution. The pacifier should be cleaned often and replaced regularly. For infants fed mother’s milk, pacifier introduction should be delayed until breastfeeding is well established.

The AAP recommends only the supine sleep position, because side sleeping increases the risk of SUID 2-fold relative to back sleeping. A firm crib mattress covered by a fitted sheet is the recommended sleep surface for infants. Soft bedding, such as water beds and couches, or objects in the sleep environment, such as stuffed toys, pillows, quilts, and comforters, are not safe.

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