Adriëtte Oostvogels

Boys (N=1850) Girls (N=1864) Normal weight N=1635 (88.4%) Overweight N=215 (11.6%) Normal weight N=1592 (85.4%) Overweight N=272 (14.6%) Maternal age Mean (SD) 31.4 (5.1) 29.3 (5.7)* 31.5 (4.9) 29.5 (5.9)* Maternal ethnicity European origin N (%) 1181 (72.2) 89 (41.4)* 1192 (74.9) 117 (43.0)* Other N (%) 454 (27.8) 126 (58.6) 400 (25.1) 155 (57.0) Maternal socioeconomic status Low N (%) 320 (19.7) 82 (38.7)* 264 (16.7) 99 (37.2)* Middle N (%) 575 (35.4) 87 (41.0) 602 (38.1) 101 (38.0) High N (%) 731 (45.0) 43 (20.3) 716 (45.3) 66 (24.8) Maternal weight status Not overweight N (%) 1177 (78.0) 106 (54.6)* 1182 (79.3) 123 (51.3)* Overweight N (%) 332 (22.0) 88 (45.4) 309 (20.7) 117 (48.7) Maternal parity Nulliparous N (%) 878 (53.7) 106 (49.3) 869 (54.6) 138 (50.7) Multiparous N (%) 757 (46.3) 109 (50.7) 723 (45.4) 134 (49.3) Maternal smoking during pregnancy Yes N (%) 158 (9.7) 30 (14.0)* 149 (9.4) 46 (16.9)* No N (%) 1476 (90.3) 185 (86.0) 1443 (90.6) 226(83.1) Gestational age at birth (days) Mean (SD) 279 (12) 278 (13) 279 (11) 279 (11) Birth weight (grams) Mean (SD) 3548 (556) 3630 (581)* 3412 (515) 3443 (542) BMI at age 5-6 years Mean (SD) 15.5 (0.8) 18.9 (1.6)* 15.4 (0.9) 19.0 (1.7)* Duration of exclusive breastfeeding a none N (%) 276 (17.7) 41 (20.3)* 250 (16.4) 57 (21.5)* <1 months N (%) 125 (8.0) 26 (12.9) 124 (8.1) 32 (12.1) 1-3 months N (%) 459 (29.4) 69 (34.2) 434 (28.5) 67 (25.3) >3 months N (%) 699 (44.8) 66 (32.7) 714 (46.9) 109 (41.1) Sleep (hours) a Mean (SD) 10.5 (0.9) 10.3 (1.1)* 10. 5 (0.9) 10.3 (1.1)* Screentime (hours) a Mean (SD) 1.5 (1.1) 1.9 (1.2)* 1.3 (0.9) 1.8 (1.2)* Member of sports club a N (%) 646 (53.6) 66 (56.9) 506 (44.0) 91 (58.3)* Table 2. Characteristics of the study population (n=3714) * p<0.05 a) measured in a subset of N=3548 (breastfeeding) and N=1309 (sleep, screen time, membership of sports club) 204 Chapter 8