What causes SIDS and how can it be prevented?

SIDS Causes and Prevention

SIDS results from a convergence of intrinsic brainstem vulnerabilities (particularly in the serotonergic system), a critical developmental period (peak at 1-4 months), and external stressors like unsafe sleep environments—but the most critical actionable factor is eliminating modifiable risk factors through evidence-based safe sleep practices. 1

Understanding the Underlying Mechanisms

The Triple-Risk Model

SIDS occurs when three factors converge simultaneously 1:

• Intrinsic vulnerability: Brainstem abnormalities in the medullary serotonergic (5-HT) system are found in up to 70% of SIDS cases, affecting respiratory, arousal, and autonomic control 1
• Critical developmental window: 90% of cases occur before 6 months of age, with peak incidence between 1-4 months when circadian rhythms and autonomic control are rapidly developing 1
• External stressors: Unsafe sleep environments, smoke exposure, and other modifiable factors trigger the fatal event 1

Pathophysiology

When these factors align, the infant experiences progressive asphyxia, bradycardia, hypotension, and metabolic acidosis, with failed arousal responses leading to death 1.

Evidence-Based Prevention Strategies

Sleep Position and Environment (Highest Priority)

Place infants supine (on their back) for every sleep period—this is the single most effective intervention. 2

• Avoid prone sleeping: Prone position dramatically increases SIDS risk and is associated with overheating 2
• Avoid side sleeping: Side sleeping carries significant risk (adjusted OR = 6.57) compared to supine position and should be discouraged 3
• Use a firm sleep surface: Soft surfaces like waterbeds, sofas, couches, or armchairs increase suffocation risk 2
• Keep the crib bare: Remove all soft objects, loose bedding, pillows, quilts, comforters, and bumper pads 2
• Room-sharing without bed-sharing: Infant should sleep in parents' room on a separate surface for at least the first 6 months 2

Bed-Sharing: Critical Warnings

Never bed-share under these high-risk circumstances 2:

• Infant younger than 3 months (regardless of other factors) 2
• Either parent smokes (adjusted OR = 5.01-5.02 when combined with bed-sharing) 3
• Parent consumed alcohol or drugs that impair alertness 2
• Parent is excessively tired 2
• Soft sleep surface (waterbed, couch, armchair) 2
• Bed-sharing with anyone other than parents 2

Tobacco, Alcohol, and Drug Exposure

Eliminate all smoke exposure—maternal smoking during pregnancy is identified as a major risk factor in almost every SIDS study, and one-third of SIDS deaths could be prevented by eliminating maternal smoking. 2

• Prenatal smoking: Dose-dependent effect on SIDS risk; affects infant arousal mechanisms 2
• Postnatal smoke exposure: Separate independent risk factor even when not smoking in bed 2
• Maternal alcohol use: First-trimester binge drinking carries adjusted OR of 8.2 for SIDS 2
• Maternal alcoholism diagnosis: Associated with adjusted hazard ratio of 6.92-8.61 for SIDS 2
• Cannabis use: Maternal use associated with adjusted OR of 2.35 for nighttime SIDS 2
• Avoid all illicit drugs: Particularly dangerous when combined with bed-sharing 2

Temperature Regulation

Avoid overheating and overbundling—dress infant in no more than one layer more than an adult would wear in that environment. 2

• Monitor for signs of overheating: sweating or chest feeling hot to touch 2
• Avoid head covering during sleep 2
• Prone sleeping position increases overheating risk 2

Protective Factors

Breastfeed exclusively for 6 months if possible—breastfeeding is associated with reduced SIDS risk. 2, 1

Offer a pacifier at sleep time—pacifier use is protective even if it falls out after infant falls asleep. 2, 1

• For breastfed infants, delay pacifier introduction until breastfeeding is firmly established (3-4 weeks) 2
• Do not force pacifier if infant refuses 2
• Never hang pacifier around infant's neck due to strangulation risk 2
• Protective effect persists throughout sleep period even after pacifier falls out 2

Ensure routine immunizations according to AAP/CDC schedule—vaccination may have a protective effect against SIDS. 2, 1

Prenatal Care

Pregnant women should obtain regular prenatal care—substantial epidemiologic evidence links regular prenatal care with lower SIDS risk. 2

Common Pitfalls to Avoid

• Using commercial devices claiming to reduce SIDS risk: Wedges, positioners, and in-bed co-sleepers are not recommended and may increase risk 2
• Relying on home cardiorespiratory monitors: These have not been documented to reduce SIDS risk 2
• Assuming "just this once" is safe: Inconsistent pacifier use (usually used but not used for last sleep) may paradoxically increase risk 2
• Thinking side sleeping is safe: Side position carries significantly elevated risk compared to supine 3

Supervised Tummy Time

Provide supervised, awake tummy time daily to prevent positional plagiocephaly and facilitate motor development—but always place infant supine for sleep. 2