Supplementary Material for: Association of maternal cigarette smoking with neonatal death: a population-based cohort study

Background: Maternal pregnancy smoking have adverse perinatal outcomes and the relationship between maternal smoking and neonatal death have not been fully elucidated. We aimed to examine the risk of neonatal death in relation to maternal smoking and to quantify potential mediators of these associations. Methods: We did a population-based cohort study using Period Linked Birth-Infant Death data from 2016 to 2019 in the US National Vital Statistics System. The exposure was maternal smoking status. The main outcome was neonatal death. Association between maternal smoking and neonatal death was estimated through logistic regression. Mediation analysis was performed to assess the extent to which the association between maternal smoking and neonatal death was mediated by neonatal complications. Results: The final sample consisted of 14717020 mothers with live singleton births. The overall neonatal mortality rate was 2.2 per 1000 live births. Maternal pregnancy smoking was associated with an increased risk of neonatal death (aOR, 1.33 [95%CI, 1.28-1.38]; P<.001), while smoking cessation during the whole pregnancy showed a comparable risk of neonatal death with non-smokers (aOR,1.06 [95%CI, 0.99-1.14]; P=0.116). Mediation analysis indicated that the association between pregnancy smoking and neonatal death might be mainly mediated by preterm birth and low Apgar score at 5min. Conclusions: Maternal pregnancy smoking, regardless of pregnancy trimester and intensity, was associated with increased risk of neonatal death. Efforts are needed for policymakers to promote smoking cessation before pregnancy and professional perinatal care should be provided for those who smoked during pregnancy.