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 ).
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)
- 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 (< 20 years), low socioeconomic status, etc.
- 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.
- Congenital anomalies that could lead to infant death (e.g., cardiac anomalies)
- Intentional suffocation; evidence of
The differential diagnoses listed here are not exhaustive.
- During pregnancy
Protective factors after birth
- The infant should be placed to sleep in the supine position
- Safe sleep environment: firm mattress; no pillows, blankets, stuffed animals, or bumper pads in the crib.
- In the first 6 months, co-sleeping in the same room without bed-sharing
- Second-hand smoke and overheating should be avoided
- Use of pacifier during sleep 
- Breastfeeding until the 4th–6th month
- "Tummy time"
- Immunization in line with the official schedule