Sudden Unexpected Infant Death (SUID) & Sudden Infant Death Syndrome (SIDS)

Key Features

• Sudden, unexplained death of an infant or child

• Sudden unexpected infant death (SUID) is gaining favor as preferred term to refer infant deaths that were classified as sudden infant death syndrome (SIDS)

• SUID

  • Defined as any sudden and unexpected infant death, whether explained (such as accidental suffocation or strangulation) or unexplained (such as SIDS)

  • Includes deaths due to infection, ingestions, metabolic diseases, cardiac arrhythmias, and trauma

  • New evidence shows that the incidence of accidental suffocation and strangulation in bed is increasing due to unsafe sleep surfaces and environments

• SIDS

  • Neither a true diagnosis nor a syndrome

  • Defined as the sudden death of an infant younger than 1 year that remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history

  • Postmortem examination is an important feature of the definition because approximately 20% of cases of sudden death can be explained by autopsy findings

Epidemiology

• Deaths peak between ages 2 and 4 months

• Most deaths occur between midnight and 8:00 AM

• SUID is more common among ethnic and racial minorities and socioeconomically disadvantaged populations

• Racial disparity in the prevalence of prone positioning and especially in bed-sharing may be contributing to the continued disparity in SUID rates between black and white infants

• There is a 3:2 male predominance in most series

• Other risk factors

  • Premature birth

  • Low birth weight

  • Recent infection

  • Young maternal age

  • Maternal tobacco or drug use

  • High maternal parity

  • Crowded living conditions

Clinical Findings

• The most consistent pathologic findings in SUID deaths from unknown cause (previously classified as SIDS) are intrathoracic petechiae and mild inflammation and congestion of the respiratory tract

• More subtle pathologic findings include

  • Brainstem gliosis

  • Extramedullary hematopoiesis

  • Increases in peri-adrenal brown fat

• When a distinct cause cannot be identified, the mechanism or mechanisms of death in SUID are unknown; hypotheses include

  • upper airway obstruction

  • catecholamine excess

  • increased fetal hemoglobin

  • Maldevelopment or delayed maturation of the brainstem, which is responsible for arousal from sleep, remains the predominant theory

• A history of mild symptoms of upper respiratory infection before death is not uncommon

Prevention

• Modifiable risk factors include

  • Sleep position, location, and environment

  • Formula feeding

  • Maternal smoking or drug use

  • Infant overheating

• The prone sleep position may increase the risk of SUID through decreased arousal or rebreathing of exhaled gases

• Side positioning, often used in hospitals and then mimicked at home, increases risk of SUID compared with the supine position and is not a safe alternative to supine sleep, even in infants with reflux

• Environmental smoke exposure, especially prenatal maternal smoking, increases the risk of SUID

• Risk of SUID is lower when an infant is breastfed and when a pacifier is offered at naptime and bedtime