Maternal use of snus as smokeless tobacco in pregnancy and infant lung function

Background Smoking in pregnancy has detrimental effects on infant respiratory health, while the effects of other nicotine-containing products on infant lung function are unclear. We aimed to explore if smokeless tobacco such as snus used in pregnancy increased the risk of lower lung function in infancy and if the associations differed by sex. Methods From the Scandinavian population-based Preventing Atopic Dermatitis and ALLergies in Children birth cohort, we included 1163 infants with available tidal flow-volume measurements at 3 months of age and maternal self-reported use of nicotine-containing products in pregnancy. The risk of a ratio of time to peak tidal expiratory flow to total expiratory time < 25th percentile by any nicotine exposure, snus exclusively and cigarette smoking with or without other nicotine-containing products was explored by regression analyses adjusting for maternal age, education and asthma. Results Overall 120 out of 1163 (10.3%) infants were exposed to any nicotine in utero, 71 out of 120 by snus exclusively and 49 out of 120 by smoking, with six also exposed to snus. By pregnancy week 6, 85.8% of mothers reported stopping nicotine use. The risk of lower lung function was higher in children exposed in utero to nicotine-containing products with an odds ratio (OR) of 1.63 (95% confidence interval (CI) 1.02-2.59) with a similar tendency for snus exclusively (OR 1.55, 95% CI 0.88-2.71) and smoking (OR 1.79, 0.84-3.84). Effect estimates were similar after adjusting for covariates. No differences of the effect by sex were observed. Conclusion Our study suggests that in utero exposure to not only cigarettes, but also snus, may negatively affect infant lung function.