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. 2017 Jun 22;7(6):e015576. doi: 10.1136/bmjopen-2016-015576

Table 1.

Characteristics for girls and boys of the Fit Futures cohort at birth and four ages up to 18–20 years, The Tromsø Study, Fit Futures, observed cases*

Characteristics Girls Boys p Value
n Mean/% (SD) n Mean/% (SD)
Birth
 Birth weight (g) 443 3455.0 (576.7) 470 3601.0 (590.0) <0.001
 Birth length (cm) 419 49.4 (2.3) 454 50.2 (2.3) <0.001
 Gestational age (weeks) 393 39.7 (1.8) 430 39.6 (2.1) 0.176
 Preterm birth (before GA week 37) 15 3.8% 23 5.4% 0.292
 Ponderal index (kg/m3) 419 28.73 (2.81) 454 28.45 (2.75) 0.141
 Body mass index (kg/m2) 419 14.19 (1.49) 454 14.28 (1.52) 0.338
 Birth weight SDS 443 −0.58 (1.74) 470 −0.24 (1.32) 0.001
 Body mass index SDS 419 0.06 (1.05) 454 −0.02 (1.04) 0.265
 Birth weight group: 443 470 0.015
 Low birth weight (<2500 g) 20 4.5% 17 3.6%
 Normal birth weight (2500–4500 g) 412 93.0% 423 90.0%
 High birth weight (≥4500 g) 11 2.5% 30 6.4%
 Size for gestational age: 443 470 0.554
 Small for gestational age 49 11.1% 46 9.8%
 Appropriate for gestational age 356 80.4% 375 79.8%
 Large for gestational age 38 8.6% 49 10.4%
 Maternal age at birth 443 28.4 (5.3) 441 28.1 (5.3) 0.995
2–4 years of age
 Age (years) 328 2.6 (0.4) 350 2.6 (0.4) 0.952
 Height (cm) 328 91.2 (4.6) 350 92.7 (4.7) <0.001
 Weight (kg) 328 13.5 (1.7) 350 14.1 (1.8) <0.001
 Body mass index (kg/m2) 328 16.17 (1.39) 350 16.37 (1.30) 0.053
 Weight SDS 328 −0.12 (1.11) 350 0.16 (1.16) 0.001
 Body mass index SDS 328 −0.04 (1.17) 350 −0.07 (1.07) 0.217
5–7 years of age
 Age (years) 354 6.0 (0.4) 384 6.1 (0.4) 0.253
 Height (cm) 354 116.7 (5.3) 384 118.3 (5.3) <0.001
 Weight (kg) 352 21.8 (3.8) 384 22.2 (3.5) 0.143
 Body mass index (kg/m2) 352 15.96 (2.04) 384 15.82 (1.74) 0.304
 Weight SDS 352 0.0004 (1.10) 384 0.11 (1.02) 0.162
 Body mass index SDS 352 −0.06 (1.10) 384 −0.03 (0.98) 0.616
15–17 years of age
 Age (years) 469 16.6 (0.4) 492 16.6 (0.4) 0.325
 Height (cm) 467 164.9 (6.5) 492 176.9 (6.7) <0.001
 Weight (kg) 467 60.9 (11.5) 492 70.2 (14.4) <0.001
 Body mass index (kg/m2) 467 22.39 (3.96) 492 22.38 (4.17) 0.952
 Pubertal maturation, §girls: 464
  Early (<12.5 years) 147 31.7%
  Intermediate (12.5–13.9 years) 212 45.7%
  Late (≥14.0 years) 105 22.6%
 Pubertal maturation, §boys: 387
  Barely started (PDS 2.0–2.9) 69 17.8%
  Underway (PDS 3.0–3.9) 285 73.6%
  Completed (PDS 4.0) 33 8.5%
18–20 years of age
 Age (years) 363 18.6 (0.4) 296 18.7 (0.3) 0.105
 Height (cm) 363 165.7 (6.5) 296 179.1 (6.5) <0.001
 Weight (kg) 363 63.2 (12.0) 296 75.2 (14.6) <0.001
 Body mass index (kg/m2) 363 23.02 (4.22) 296 23.42 (4.18) 0.228

*In observed data n is varying from 659 to 961.

†p Value for sex difference was obtained by t-test or χ2 test.

‡SDS, SD scores according to Norwegian reference data.23

§Pubertal maturation is based on age of menarche in girls and according to Pubertal Development Scale (PDS) in boys; total score of four items of secondary sexual characteristics on a scale from 1 to 4 (sum of total score divided by 4). None had a score <2.0 in total score.25

GA, gestational age.