Secular trends in smoking during pregnancy according to socioeconomic position in Brazil

INTRODUCTION:  Smoking prevalence is dropping rapidly in Brazil, however little is known about how patterns are changing for different socioeconomic groups. Smoking during pregnancy is particularly hazardous both to the mother and to the fetus, being a leading cause of low birthweight and preterm delivery.

METHODS:  Four population-based studies were carried out in 1982, 1993, 2004 and 2011 in the city of Pelotas in Southern Brazil. Each study recruited all births taking place in the calendar year, with at least 4,287 births per study. Refusals were below 1%. Information was collected on family income (recoded in quintiles) and on smoking during pregnancy

RESULTS:   The overall prevalence of smoking during pregnancy fell consecutively in each survey (35.6% in 1982; 33.4% in 1993; 24.3% in 2004 and 20.7% in 2011), corresponding to a 41% reduction in this 29-year period. In each year, prevalence decreased monotonically with increasing income (P<0.001). In the poorest quintile, the overall reduction was equal to 27.1% (from 43.9% in 1982 to 32.0% in 2011); in the wealthiest quintile the reduction was of 67.1% (from 25.8% to 8.5%). There was a significant interaction between study year and income quintile. The slope index of inequality changed from -20.1 pct points in 1982 to -31.6 pct points in 2011, and the concentration index from -0.09 to -0.24, indicating increases in both absolute and relative inequalities.

CONCLUSIONS:  Although smoking is declining in Brazil as whole, this unique series of population-based studies from the same city shows that the reduction among the better off is far greater than among the poor.  Further efforts are needed to reduce smoking among women of reproductive age belonging to poor families.