Compared with newborns of unvaccinated women, those born to vaccinated mothers had lower odds of SGA (adjusted OR = 0.31; 95% CI, 0.13-0.75) during the period of widespread influenza activity (Table 3) . Although the magnitude of the ORs of the association between maternal influenza vaccine and SGA generally increased with the increase in the intensity of influenza activity, these associations were not statistically significant (other than for the period of widespread activity) ( Table 3 ). The associations observed in the secondary multivariate models using the traditional approach were qualitatively similar to the associations in the primary multivariate models (Tables 2 and 3) .