Sudden infant death syndrome

Sudden infant death syndrome (SIDS) is the abrupt and unexplained death of an infant less than 1 year old. Although the etiology of SIDS remains unclear, evidence suggests that it is caused by a combination of environmental triggers and cardiorespiratory impairment, which then leads to prolonged hypoxia. Most SIDS cases occur in the first 6 months of life. Parents should receive information on how to prevent SIDS during prenatal care and in pediatric check-ups after birth: Recommendations include placing the infant on his/her back to sleep, ensuring a safe sleep environment, and avoiding overheating and second-hand smoke. SIDS is a diagnosis of exclusion; an autopsy is therefore important to rule out differential diagnoses (e.g., congenital cardiac anomalies or battered child syndrome).

• Peak incidence: 2–6 months ; in rare cases, during the first days of life
• Sex: ♂ > ♀

References:^[2]

Epidemiological data refers to the US, unless otherwise specified.

The etiology of SIDS remains unclear. Evidence suggests that it is caused by a combination of both extrinsic and intrinsic factors, which ultimately lead to acute or chronic hypoxia. Over 90% of cases of SIDS occur during sleep.

Extrinsic factors (triggers)

• Sleeping in the prone position
• Exposure to nicotine during pregnancy and after birth (including 2nd-hand smoking)
• Overheating
• Unsafe sleeping environment or CO₂ rebreathing: e.g., a shared blanket, stuffed animals in the crib (because of the grasping reflex, newborns tend to drag items to their faces)
• Many more correlations: SIDS in siblings, babies born prematurely, young mothers (< 16 years), low socioeconomic status, etc.

Intrinsic factors

• Brainstem disorder that includes morphologic/biochemical abnormalities of serotonin (known as 5-hydroxytryptamine or 5-HT), which impacts the respiratory drive, the ability to wake up, blood pressure, upper respiratory reflexes , and body temperature.

References:^[3]

SIDS is a diagnosis of exclusion. If there is an unexplained death of an apparently healthy infant, an autopsy is required by law to rule out other causes of death.

• Congenital anomalies that could lead to infant death (e.g., cardiac anomalies)
• Intentional suffocation; evidence of battered child syndrome

The differential diagnoses listed here are not exhaustive.