Maternal smoking is associated with increased risk of sudden unexpected infant death

1. Maternal smoking behaviour increased the risk of Sudden Unexpected Infant Death, with the highest risk among those who continuously smoked during pregnancy.

Evidence Rating Level: 2 (Good)

Sudden Unexpected Infant Death (SUID) involves sleep-related deaths during infancy that are due to sudden infant death syndrome, accidental suffocation or strangulation in bed, and other unknown causes. While maternal smoking during pregnancy is an important risk factor for SUID, the impact of variations in smoking behaviours (e.g. timing, intensity, and cessation) is unclear. This study thus examined the association between maternal smoking and SUID, while incorporating categorizations of smoking behaviours. This retrospective cohort study using data from the Centre for Disease Control Linked Birth-Infant Death files included singleton live births (birth weight >1000 g, gestational age >25 weeks) in the US occurring between January 1, 2017, and December 31, 2021, and infant deaths within the first year of life. The primary exposure was maternal smoking behaviour, categorized into non-smoking, pre-pregnancy smoking only, trimester-specific smoking, continuous or discontinuous smoking, and cessation before the third trimester, with stratification by smoking intensity (heavy vs light smoker). This study included 16,484,245 live births. In total, 15,222,196 (92%) patients were non-smokers, 664,741 (4%) were heavy smokers who continuously smoked during their pregnancy, 234,259 (1.4%) were heavy smokers who only smoked during pre-pregnancy, and 154,618 (0.94%) were heavy smokers who ceased smoking before their third trimester. After adjusting for socio-economic disparities and key pregnancy and infant factors, heavy continuous smokers had the highest odds for SUID (aOR 2.81, 95% CI 2.67–2.94), followed by light continuous smokers (aOR 2.47, 95% CI 2.19–2.78) and discontinuous heavy smokers (aOR 2.29, 95% CI 1.72–3.00) compared with non-smokers. Pre-pregnancy-only smokers had the lowest odds of SUID among all smoking categories (light smoker: aOR 1.77, 95% CI 1.48–2.10; heavy smoker: aOR 1.61, 95% CI 1.44–1.78). There were no differences found between heavy and light smokers for any category. Overall, this study found that maternal smoking behaviour increased the risk of SUID, with the highest risk among those who continuously smoked during pregnancy. Future research should examine other substance use and their potential interactions with smoking to understand the combined effects. 

Click here to read this study in PLOS One

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