Adriëtte Oostvogels

8 203 Growth patterns to overweight and maternal weight status are strong determinants of postnatal growth, both influenced by ethnicity 17 and SES 15,16 and are therefore part of the causal pathway. Descriptive analyses were performed in SPSS version 23 and growth patterns were analyzed with R version 3.3.3. Results Study population In our study population 13.1% of the children were overweight. Boys and girls with overweight had respectively a 3.4 kg/m 2 and 3.6 kg/m 2 higher BMI than normal weight children at age 5-6 years. Overweight was more prevalent in girls (14.6%) than in boys (11.6%) and in children with a non-European origin (24.8%) and low SES (15.6%) background (Table 1). Children with overweight more often had mothers who were younger, more often overweight themselves, multiparous and smoked more often than the mothers of normal weight children (Table 2). Figure 2 presents the average BMI growth curves of children with normal weight and overweight at age 5-6 years. Overweight boys at age 5-6 years had a higher weight and BMI at birth compared to normal weight boys (Table 3 and Supplementary Table 2). In overweight children, the BMI peak was higher (±1 kg/m 2 ) than for normal weight children. Although timing of the BMI peak was earlier in overweight boys than in normal weight boys, no differences were seen in girls. On the other hand, timing of the adiposity rebound was earlier in overweight children (at age 3 years) than in normal weight children (at age 5 years). The magnitude of the drop in BMI after the BMI peak differed between overweight boys (ΔBMI= ±1 kg/m 2 ) compared to normal weight boys (ΔBMI=±2 kg/m 2 ), but in girls no differences were found: ΔBMI= ±1.5 kg/m 2 for both. Total study population (N=3714) Boys (N=1850) Girls (1864) Total study population 13.1% 11.6% 14.6% Ethnicity European origin 8.0% 7.0% 8.9% Other 24.8% 21.7% 27.9% Socioeconomic status (only European origin) High SES 6.3% 4.9% 7.6% Middle SES 8.9% 8.3% 9.4% Low SES 15.9% 16.1% 15.7% Table 1. Prevalence of overweight in our study population