Table 1 Table of covariate distribution on category of infancy weight gain
|  | Slow (n = 3796) | Mean (n = 9300) | Rapid (n = 3800) | Very rapid (n = 2998) | Total (n = 19,894) | X2 p-value |
|---|---|---|---|---|---|---|
Child sex, n (%) | ||||||
 Male | 1919 (50.6) | 4668 (50.2) | 1930 (50.8) | 1624 (54.2) | 10,141 (51.0) |  |
 Female | 1877 (49.4) | 4632 (49.8) | 1870 (49.2) | 1374 (45.8) | 9753 (49.0) | 0.002 |
Size for gestational age at birth, n (%) | ||||||
 SGA | 33 (0.9) | 398 (4.3) | 378 (10.0) | 487 (16.3) | 1296 (6.5) |  |
 AGA | 2574 (67.9) | 7872 (84.7) | 3246 (85.6) | 2431 (81.2) | 16,123 (81.1) |  |
 LGA | 1185 (31.2) | 1022 (11.0) | 170 (4.5) | 74 (2.5) | 2451 (12.3) | < 0.0001 |
 Missing | 4 | 8 | 6 | 6 | 24 |  |
Gestational age at birth, n (%) | ||||||
 37 weeks | 52 (1.4) | 296 (3.2) | 262 (6.9) | 392 (13.1) | 1002 (5.0) |  |
 38 weeks | 284 (7.5) | 1106 (11.9) | 664 (17.5) | 778 (26.0) | 2832 (14.3) |  |
 39 weeks | 713 (18.8) | 2244 (24.1) | 978 (25.8) | 713 (23.8) | 4648 (23.4) |  |
 40 weeks | 1327 (35.0) | 3057 (32.9) | 1131 (29.8) | 694 (23.2) | 6209 (31.2) |  |
 41 weeks | 1416 (37.3) | 2589 (27.9) | 759 (20.0) | 415 (13.9) | 5179 (26.1) | < 0.0001 |
 Missing | 4 | 8 | 6 | 6 | 24 |  |
Mode of delivery, n (%) | ||||||
 Caesarean section | 706 (18.6) | 1751 (18.8) | 788 (20.7) | 719 (24.0) | 3964 (19.9) |  |
 Vaginal | 3090 (81.4) | 7549 (81.2) | 3012 (79.3) | 2279 (76.0) | 15,930 (80.1) | < 0.0001 |
Parity, n (%) | ||||||
 1 | 1448 (38.2) | 4694 (50.6) | 2191 (57.9) | 1871 (62.7) | 10,204 (51.4) |  |
 2 | 1699 (44.8) | 3410 (36.8) | 1187 (31.4) | 781 (26.2) | 7077 (35.7) |  |
  > 2 | 643 (17.0) | 1171 (12.6) | 408 (10.8) | 334 (11.2) | 2556 (12.9) | < 0.0001 |
 Missing | 6 | 25 | 14 | 12 | 57 |  |
Maternal pre-pregnancy BMI, n (%) | ||||||
 Underweight | 126 (3.3) | 358 (3.9) | 146 (3.9) | 125 (4.2) | 755 (3.8) |  |
 Normal weight | 2311 (61.2) | 5862 (63.4) | 2363 (62.7) | 1850 (62.0) | 12,386 (62.7) |  |
 Overweight | 816 (21.6) | 1859 (20.1) | 767 (20.4) | 616 (20.7) | 4058 (20.5) |  |
 Obesity I | 348 (9.2) | 768 (8.3) | 313 (8.3) | 271 (9.1) | 1700 (8.6) |  |
 Obesity II + III | 173 (4.6) | 396 (4.3) | 179 (4.8) | 120 (4.0) | 868 (4.4) | 0.23 |
 Missing | 22 | 57 | 32 | 16 | 127 |  |
Maternal smoking during pregnancy, n (%) | ||||||
 Yes | 140 (3.7) | 459 (5.0) | 283 (7.5) | 302 (10.2) | 1184 (6.0) |  |
 Stopped during pregnancy | 108 (2.9) | 318 (3.4) | 141 (3.7) | 116 (3.9) | 683 (3.5) |  |
 No | 3516 (93.4) | 8454 (91.6) | 3338 (88.7) | 2545 (85.9) | 17,853 (90.5) | < 0.0001 |
 Missing | 32 | 69 | 38 | 35 | 174 |  |
Gestational diabetes, n (%) | ||||||
 Yes | 136 (3.6) | 321 (3.5) | 143 (3.8) | 104 (3.5) | 704 (3.5) |  |
 No | 3660 (96.4) | 8979 (96.5) | 3657 (96.2) | 2894 (96.5) | 19,190 (96.5) | 0.84 |
Duration of breastfeeding, n (%) | ||||||
 0–2 months | 589 (22.4) | 1566 (24.9) | 761 (30.2) | 732 (37.6) | 3648 (27.3) |  |
 2–4 months | 455 (17.3) | 1121 (17.8) | 461 (18.3) | 348 (17.9) | 2385 (17.8) |  |
 4–6 months | 1164 (44.3) | 2687 (42.7) | 973 (38.7) | 644 (33.1) | 5468 (40.9) |  |
  > 6 months | 418 (15.9) | 919 (14.6) | 321 (12.8) | 222 (11.4) | 1880 (14.0) | < 0.0001 |
 Missing | 1170 | 3007 | 1284 | 1052 | 6513 |  |
Level of maternal education, n (%) | ||||||
 ISCED 0–2 | 1345 (35.4) | 3729 (40.1) | 1744 (45.9) | 1435 (47.9) | 8253 (41.5) |  |
 ISCED 4 | 885 (23.3) | 2054 (22.1) | 807 (21.2) | 633 (21.1) | 4379 (22.0) |  |
 ISCED 5–6 | 996 (26.2) | 2230 (24.0) | 771 (20.3) | 579 (19.3) | 4576 (23.0) |  |
 ISCED 7–8 | 570 (15.0) | 1287 (13.8) | 478 (12.6) | 351 (11.7) | 2686 (13.5) | < 0.0001 |
Household income (quartiles), n (%) | ||||||
 Low | 727 (19.2) | 2202 (23.7) | 1019 (26.8) | 884 (29.5) | 4832 (24.3) |  |
 Low-middle | 921 (24.3) | 2331 (25.1) | 965 (25.4) | 741 (24.7) | 4958 (24.9) |  |
 High-middle | 1052 (27.7) | 2406 (25.9) | 925 (24.3) | 708 (23.6) | 5091 (25.6) |  |
 High | 1096 (28.9) | 2361 (25.4) | 891 (23.4) | 665 (22.2) | 5013 (25.2) | < 0.0001 |
Overweight or obesity at follow-up, n (%) | ||||||
 Yes | 95 (2.5) | 470 (5.1) | 395 (10.4) | 537 (17.9) | 1497 (7.5) |  |
 No | 3701 (97.5) | 8830 (94.9) | 3405 (89.6) | 2461 (82.1) | 18,397 (92.5) | < 0.0001 |