Pelotas cohort studies.

Two SEP indicators were used: family income and maternal education. In ALSPAC, family income per week was collected at 33 months after delivery. In the 1982 and 1993 Pelotas cohort studies family income of the month prior to the interview was collected in the perinatal interview. To allow comparisons between studies, quintiles of family income were calculated in each study. In the 1993 Pelotas cohort study, family income was collected as a continuous variable (in Reales) and quintiles were calculated directly. In ALSPAC and in the 1982 Pelotas cohort study, family income was collected as a grouped variable. A principal components analysis was carried out in ALSPAC and the 1982 Pelotas cohort studies and the first component was used to derive a score that was usedamong those whose mothers had more years of schooling. In ALSPAC higher prevalence of overweight was seen among boys whose mothers had lower educational achievement but no robust association was found between overweight and family income. Among 11 year-old girls overweight was associated with both SEP indicators. However, while in the 1993 Pelotas cohort study there was a positive association (higher prevalence of overweight in the higher socioeconomic and educational strata), an inverse association (higher prevalence of overweight among the poorest and among daughters of women with the lowest educational achievement) was found in ALSPAC.

![**Distribution of overweight prevalence rates by SEP among 11 year-olds, ALSPAC and 1993 Pelotas cohorts**. Overweight: Body mass index \> 1 standard deviation according to WHO\'s growth charts of BMI-for-age and sex (obese children