Effect of Swedish snuff (snus) on preterm birth

Abstract

Objective: To compare the effects of Swedish snuff and cigarette smoking on risks of preterm birth.

Design: Population-based cohort study.

Setting: Sweden.

Population: All live, singleton births in Sweden 1999-2006.

Methods: Odds ratios (OR) with 95% confidence intervals (CI) were used to estimate relative risks for preterm birth in snuff users (n = 7607), light smokers (1-9 cigarettes/day; n = 41 436) and heavy smokers (ten or more cigarettes/day; n = 16 951) using non-tobacco users (n = 503 957) as reference.

Main outcome measures: Very (<32 weeks) and moderately (32-36 weeks) preterm birth.

Results: Compared with non-tobacco users, snuff users had increased risks of both very (adjusted OR 1.38; 95% CI 1.04-1.83) and moderately (adjusted OR 1.25; 95% CI 1.12-1.40) preterm birth. Compared with non-tobacco users, light smokers had increased risks of both very (adjusted OR 1.60; 95% CI 1.42-1.81) and moderately (adjusted OR: 1.18; 95% CI: 1.12-1.24) preterm birth, and heavy smokers had even higher risks. Among smokers, but not among snuff users, the risk was more pronounced for spontaneous than induced preterm birth.

Conclusions: The use of Swedish snuff was associated with increased risks of very and moderately preterm birth with both spontaneous and induced onsets. Swedish snuff is not a safe alternative to cigarette smoking during pregnancy.