['Although there is convincing evidence for the association between small for gestational age (SGA) and socioeconomic status (SES), it is not known to what extent explanatory factors contribute to this association.', 'To examine to what extent risk factors could explain educational inequalities in SGA.', 'In this study fully completed data were available for 3793 pregnant women of Dutch origin from a population-based cohort (ABCD study). Path-analysis was conducted to examine the role of explanatory factors in the relation of maternal education to SGA.', 'Low-educated pregnant women had a higher risk of SGA offspring compared to the high-educated women (OR 1.98, 95% CI 1.35-2.89). In path-analysis, maternal cigarette smoking and maternal height explained this association. Maternal age, hypertension, chronic disease, late entry into antenatal care, neighborhood income, underweight, environmental cigarette smoking, drug abuse, alcohol use, caffeine intake, fish intake, folic acid intake, anxiety, and depressive symptoms did not play a role in the association between maternal education and SGA birth.'] Does smoking overrule many other risk factors for small for gestational age birth in less educated mothers?