Maternal smoking before and after pregnancy: effects on behavioral outcomes in middle childhood

The aim of this research was to examine the extent to which maternal smoking before and after pregnancy was associated with childhood disruptive behaviors when due allowance was made for potentially confounding factors which may have been associated with both maternal smoking habits and childhood problem behaviors.

During the course of a 15-year longitudinal study of a birth cohort of 1265 New Zealand children, the following measures were obtained: (1) measures of daily cigarette intake during pregnancy and after pregnancy; (2) measures of childhood disruptive behaviors including conduct problems and attention deficit behaviors based on both maternal and teacher report data; and (3) measures of a series of potentially confounding family, social, parental, and related factors.

Before adjustments for confounding, maternal smoking both before and after pregnancy was found to be associated with significant increases in rates of childhood problem behaviors: children whose mothers smoked in excess of 20 cigarettes per day had mean problem behavior scores that were between 0.16 and 0.56 standard deviations higher than those of children whose mothers were nonsmokers. The results were then adjusted using regression methods to take account of (1) correlations between pregnancy and postpregnancy smoking and (2) potentially confounding factors. The results of regression adjustment suggested that maternal smoking during pregnancy was associated with small but statistically detectable increases in rates of childhood problem behaviors, with children whose mothers smoked in excess of 20 cigarettes per day having mean scores that were 0.10 to 0.36 standard deviations higher than those of the offspring of nonsmokers, even after adjustment for a series of confounding factors. However, smoking after pregnancy was not significantly associated with increased rates of childhood problem behavior after adjustment for sources of confounding.

The results are generally consistent with the hypothesis that smoking during pregnancy may be associated with small but detectable increases in the risks of problem behaviors in childhood. This suggests that possible adverse effects on childhood behavioral adjustment should be added to the growing list of adverse consequences of parental smoking for childhood health and well-being.