Temporal trends in social disparities in maternal smoking and breastfeeding in Canada, 1992-2008.

A steady decrease in maternal smoking during pregnancy and a steady increase in breastfeeding rates have been observed in Canada in the past two decades. However, the extent to which all socioeconomic classes have benefited from this progress is unknown. Therefore, this study was undertaken to determine: (1) whether progress achieved benefited the entire population or was limited to specific strata; and (2) whether disparities among strata decreased, stayed the same, or increased over time. We used data from the National Longitudinal Survey of Children and Youth, which enrolled children aged 0-3 years between 1994 and 2008. Data collected at entry was analyzed in a cross-sectional manner. Between birth years 1992-1996 and 2005-2008, smoking during pregnancy decreased from 11.5 % (95 % CI 10.0-13.0 %) to 5.2 % (95 % CI 4.1-6.3 %) among mothers with a college or university degree and from 43.0 % (95 % CI 38.8-47.2 %) to 38.6 % (95 % CI 32.9-44.2 %) among those with less than secondary education. During the same period, the rate of breastfeeding initiation increased from 83.8 % (95 % CI 81.9-85.6 %) to 91.5 % (95 % CI 90.2-92.8 %) among mothers with a college or university degree and from 63.1 % (95 % CI 58.9-67.4 %) to 74.7 % (95 % CI 69.8-79.7 %) among those with less than secondary education. The risks of smoking and of not breastfeeding remained significantly higher in the least educated category than in the most educated throughout the study period, and these associations remained statistically significant after controlling for maternal age. Gaps between the least and the most educated mothers narrowed for breastfeeding but widened for smoking during pregnancy.