Examining differences between the chosen study population and the other MoBa children who had reached 36 months of age at the time of the current study and were born before the end of 2007 but for whom we did not have information from all the questionnaires used in the present study, we found that the study population contained fewer children with mothers in the youngest age group, fewer children of single mothers, fewer children of mothers who smoked during pregnancy, more children of first-time mothers, and more children of mothers with some university-level education. Compared with other MoBa children, those in the study population also had lower birth weights and shorter gestational ages and were more likely to have been delivered by cesarean section.