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 cases of SIDS 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 their back to sleep, ensuring a safe sleep environment (e.g., appropriate sleeping surface and sleepwear, room-sharing with a caretaker, avoiding accessories like pillows and toys) avoiding overheating, and avoiding second-hand smoke. SIDS is a diagnosis of exclusion, and autopsy is required to rule out other causes of death (e.g., congenital cardiac anomalies or ).
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 
- Sleeping in the prone position
- Exposure to nicotine during pregnancy and after birth (including 2nd-hand smoking)
- Young maternal age (especially < 20 years)
- Unsafe sleeping environment or CO2 rebreathing, e.g., a shared blanket, stuffed animals in the crib, soft bedding
Intrinsic factors 
- Congenital anomalies (e.g., cardiac anomalies)
- Fatal child abuse
- Metabolic disease (e.g., MCAD deficiency)
- Infections (e.g., pneumonia, meningitis, sepsis)
- Aspiration, asphyxiation
The differential diagnoses listed here are not exhaustive.
- Definition: a sudden, brief (< 1 minute), and resolved event without apparent cause occurring in a child < 1 year and involving ≥ 1 of the following:
The presence of all the following criteria indicates a low risk of adverse outcomes, recurrence, and serious underlying conditions:
- Age > 60 days
- Gestational age ≥ 32 weeks and corrected gestational age ≥ 45 weeks
- Event lasted < 1 minute
- First BRUE
- No CPR by a trained medical provider required
- No concerning signs or symptoms on physical examination (e.g., bruising, choking, coughing)
- No concerning history (e.g., feeding problems, apneas)
- Patients who do not meet all of the criteria should be considered at high risk for adverse outcomes, recurrence, and serious underlying conditions.
- The presence of all the following criteria indicates a low risk of adverse outcomes, recurrence, and serious underlying conditions:
Patients with low-risk BRUE 
- Education for caregivers
- Recommend CPR training to caregivers
- Patients with high-risk BRUE 
- Initial evaluation and management
Secondary evaluation and management
- If no cause can be established after primary evaluation, hospital admission for continuous prolonged oximetry, observation, swallow evaluation, and feeding consultation is indicated.
- Further interventions according to event characteristics
- Patients with low-risk BRUE 
Prenatal and well-child care visits should involve education on how to prevent SIDS.
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 
- Smoke-free environment
- Avoid overheating
- Use of pacifier during sleep, especially between 1 and 6 months of age 
- Breastfeeding until at least the age of 4 months 
- Placing an infant in a prone position while awake and supervised (tummy time) helps strengthen neck and shoulder muscles.
- Immunization in line with the official vaccination schedule to prevent infections associated with SIDS