Smoking during pregnancy was up to 70% more common in the most deprived municipalities - a multilevel analysis of all singleton births during 2005-2010 in Finland.

Objective: We investigated whether there was an association between maternal smoking habits during pregnancy and municipality level deprivation defined based on education, income and unemployment after adjustment for individual level covariates, including socioeconomic status (SES), in Finland, a Nordic welfare state.

Methods: Data were gathered from the Medical Birth Register and comprised all singleton births (n=337,876) during 2005-2010. To account for any correlation of women clustered within a municipality, we fitted generalized estimating equation (GEE) models.

Results: In total, 15.3% of the women with singleton pregnancies smoked during pregnancy. After adjustment for individual level confounders, smoking during pregnancy was 5.4-fold higher among women with the lowest as compared with highest individual SES. Controlling for individual SES, age and year of birth, women living in municipalities defined as intermediately and highly deprived based on education were 53.7% (adjusted odds ratio [aOR] 1.537, 95% confidence interval [CI] 1.493-1.583) and 71.5% (aOR 1.715, 95% CI 1.647-1.785), respectively, more likely to smoke during pregnancy than women in the least deprived municipalities.

Conclusions: Individual SES is the strongest correlate of smoking during pregnancy but conditional on individual variables; lower municipality aggregate education is associated with up to 70% higher smoking prevalence.