Changes in snuff and smoking habits in Swedish pregnant women and risk for small for gestational age births

Objective To examine associations between antenatal exposure to Swedish oral moist snuff (which includes essentially only nicotine) and to smoking and risks of small-for-gestational-age (SGA) births and to compare risks among women who stopped or continued using snuff or smoking during pregnancy. Design Population-based cohort study. Setting Sweden. Population All live singleton births in Sweden 19992010. Methods Odds ratios (OR) with 95% confidence intervals (CI) were calculated using multiple logistic regression analysis. Main outcome measures SGA birth, also stratified into preterm (36weeks of gestation) and term (37weeks of gestation) SGA births. Results Compared with non-tobacco users in early pregnancy, snuff users and above all smokers in early pregnancy had increased risks of SGA births: adjusted ORs (95% CI) were 1.26 (1.091.46) and 2.55 (2.432.67), respectively). Snuff use had, if anything, a stronger association with preterm SGA than term SGA, whereas the opposite was true for smoking. Compared with non-tobacco users, women who stopped using snuff before their first visit to antenatal care had no increased risks of preterm or term SGA, and women who stopped using snuff later during pregnancy had no increased risk of term SGA. Smoking cessation early in pregnancy was associated with a larger reduction in risk than smoking cessation later in pregnancy. Conclusions As both smoking and snuff use influence risk of SGA, both nicotine but above all tobacco combustion products are involved in the mechanisms by which maternal smoking increases the risk of SGA.