Table 1 Distribution/proportions of baseline characteristics by fourths of age at peak height velocity based on imputed data
Quartile 1, n (%) | Quartile 2, n (%) | Quartile 3, n (%) | Quartile 4, n (%) | |
Household social class | ||||
Professional | 182 (16.78) | 188 (17.38) | 218 (20.02) | 213 (19.67) |
Managerial/technical | 501 (46.18) | 479 (44.09) | 517 (47.64) | 514 (47.45) |
Non-manual | 248 (22.87) | 273 (25.19) | 230 (21.22) | 235 (21.75) |
Manual/part skills/unskilled | 154 (14.17) | 145 (13.34) | 121 (11.12) | 121 (11.13) |
Maternal education | 182 (16.78) | 188 (17.38) | 218 (20.02) | 213 (19.67) |
Less than O level | 217 (20.03) | 181 (16.72) | 164 (15.16) | 197 (18.18) |
O level | 372 (34.24) | 392 (36.02) | 368 (33.83) | 330 (30.51) |
A level | 298 (27.49) | 293 (27.04) | 339 (31.20) | 323 (29.80) |
Degree or above | 198 (18.24) | 219 (20.22) | 215 (19.81) | 233 (21.51) |
Mother’s partner’s education | ||||
Less than O level | 312 (28.73) | 261 (24.14) | 246 (22.64) | 237 (21.87) |
O level | 230 (21.19) | 232 (21.39) | 223 (20.52) | 250 (23.07) |
A level | 300 (27.65) | 331 (30.51) | 321 (29.56) | 300 (27.66) |
Degree or above | 243 (22.43) | 260 (23.96) | 296 (27.28) | 297 (27.40) |
Breastfeeding until 3 months | ||||
Exclusively | 389 (35.83) | 407 (37.53) | 408 (37.59) | 383 (35.35) |
Non-exclusively | 523 (48.12) | 514 (47.37) | 555 (51.12) | 570 (52.61) |
Never | 174 (16.05) | 164 (15.10) | 122 (11.29) | 130 (12.04) |
First-born child | 559 (51.51) | 506 (46.67) | 547 (50.42) | 516 (47.64) |
Maternal marital status | ||||
Never married | 143 (13.14) | 139 (12.79) | 127 (11.74) | 144 (13.29) |
Married | 883 (81.42) | 896 (82.60) | 913 (84.01) | 891 (82.28) |
Widowed/divorced/separated | 59 (5.44) | 50 (4.61) | 46 (4.25) | 48 (4.43) |
Maternal smoking status | ||||
No | 892 (82.20) | 930 (85.68) | 931 (85.82) | 924 (85.28) |
Yes | 193 (17.80) | 155 (14.32) | 154 (14.18) | 159 (14.72) |
Mean (SE) | Mean (SE) | Mean (SE) | Mean (SE) | |
Maternal age at delivery (years) | 29.25 (0.14) | 29.35 (0.14) | 29.64 (0.13) | 29.74 (0.14) |
Gestational age (weeks) | 39.54 (0.05) | 39.48 (0.05) | 39.32 (0.05) | 39.37 (0.05) |
Birthweight (kg) | 3.35 (0.01) | 3.41 (0.01) | 3.44 (0.01) | 3.50 (0.01) |
Maternal BMI (kg/m2) | 23.13 (0.11) | 22.80 (0.11) | 22.63 (0.11) | 22.70 (0.11) |
Height at age 9 (cm) | 141.36 (0.19) | 138.95 (0.19) | 139.12 (0.18) | 138.29 (0.18) |
Fat mass at age 9 (kg) | 37.52 (0.25) | 33.69 (0.21) | 33.22 (0.20) | 31.87 (0.18) |