What are the risk factors associated with Sudden Infant Death Syndrome (SIDS)?

Risk Factors Associated with Sudden Infant Death Syndrome (SIDS)

The most critical modifiable risk factors for SIDS are maternal smoking during pregnancy (which could prevent one-third of SIDS deaths if eliminated), prone or side sleeping positions, bed-sharing (especially with smokers), and exposure to alcohol or illicit drugs. 1

Sleep Position Risk Factors

• Prone (stomach) sleeping position is a major risk factor identified in nearly all epidemiologic studies, with the prone position being the most important modifiable risk factor for SIDS 2
• Side sleeping position also carries significantly increased risk compared to supine sleeping (adjusted OR = 6.57), and infants placed on their side can roll to prone position 3
• The supine (back) sleeping position is the only safe sleep position for every sleep period 1

Maternal Substance Use Risk Factors

Tobacco Smoke Exposure

• Maternal smoking during pregnancy is identified as a major risk factor in almost every epidemiologic study of SIDS, with an estimated one-third of SIDS deaths preventable if all maternal smoking during pregnancy was eliminated 1
• The effect of tobacco smoke exposure on SIDS risk is dose-dependent 1
• Postnatal smoke exposure in the infant's environment is a separate major risk factor 1
• The risk of SIDS is particularly high when the infant bed-shares with an adult smoker, even when the adult does not smoke in bed 1

Alcohol Use

• Maternal alcohol use carries an adjusted OR of 6.2 (95% CI: 1.6–23.3) for SIDS risk 1
• Maternal first-trimester binge drinking has an adjusted OR of 8.2 (95% CI: 1.9–35.3) for SIDS 1
• Maternal alcoholism diagnosis during pregnancy (adjusted hazard ratio: 6.92) or within 1 year postpregnancy (adjusted hazard ratio: 8.61) significantly increases SIDS risk 1
• At least 16.41% of SIDS deaths are attributable to maternal alcohol use disorder 1
• Parental alcohol and/or illicit drug use in combination with bed-sharing places the infant at particularly high risk of SIDS and unintentional suffocation 1

Illicit Drug Use

• Maternal cannabis use is associated with increased risk of SIDS (adjusted OR: 2.35; 95% CI: 1.36–4.05) at night 1
• In utero exposure to opiates (primarily methadone and heroin) is associated with increased SIDS risk in retrospective studies 1
• In utero cocaine exposure has generally shown increased risk in population-based studies 1

Bed-Sharing Risk Factors

• Bed-sharing with infants younger than 3 months is particularly high-risk, regardless of parental smoking status 4
• Bed-sharing with a current smoker or if the mother smoked during pregnancy dramatically increases risk 4, 3
• There is a significant interaction between maternal smoking and bed-sharing: compared with infants not exposed to either, the adjusted OR for infants of mothers who smoked was 5.01 (95% CI = 2.01,12.46) for bed-sharing 3
• Bed-sharing with someone who is excessively tired or using medications/substances that could impair alertness increases risk 4
• Sleeping on couches and armchairs places infants at extraordinarily high risk of infant death, including SIDS and suffocation 4

Sleep Environment Risk Factors

• Soft sleeping surfaces and soft bedding in the crib increase SIDS risk 1, 5
• Overheating and excessive clothing/blankets covering an infant are associated with increased SIDS risk 1, 5
• Infants who sleep in the prone position have a higher risk of overheating than supine sleeping infants 1
• Head covering in infants increases risk 1

Demographic and Prenatal Risk Factors

• Lack of regular prenatal care is associated with increased SIDS risk 1
• Preterm birth and low birth weight are risk factors for SIDS 1, 3
• Male infant sex is associated with increased risk 3
• Young maternal age and leaving school at a younger age are risk factors 3
• Unmarried mother status and greater number of previous pregnancies are associated with increased risk 3
• Late attendance for antenatal care increases risk 3

Protective Factors (Absence Increases Risk)

• Lack of breastfeeding is associated with increased SIDS risk 1, 5
• Lack of pacifier use increases risk, as pacifier use during sleep decreases SIDS risk by 50-90% 1
• Not room-sharing (infant sleeping in separate room from parents) increases risk, as room-sharing without bed-sharing decreases SIDS risk by as much as 50% 4
• Lack of routine immunizations may increase risk, as immunizations are recommended for SIDS reduction 1

Critical Clinical Pitfall

The combination of multiple risk factors exponentially increases SIDS risk. For example, bed-sharing appears to be a risk primarily to infants of mothers who smoke, and addressing bed-sharing among mothers who smoke could reduce SIDS by at least one-third 3. Similarly, prone sleeping position combined with soft bedding or overheating creates compounded risk 1.