Table 1. Characteristics of the study participants included in the analysis of maternal gluten intake during pregnancy and risk of type 1 diabetes in the child.
| Gluten intake by percentile | All participants | <10% | 10%–20% | 20%–50% | 50%–80% | 80%–90% | >90% |
|---|---|---|---|---|---|---|---|
| Median (range) in g/day | 13.0 (0–62.5) | 5.9 (0–7.6) | 8.7 (7.6–9.5) | 11.4 (9.5–13.0) | 14.8 (13.0–17.3) | 18.4 (17.3–20.1) | 23.0 (20.1–62.5) |
| Maternal characteristics | n = 86,306 | n = 8,518 | n = 8,616 | n = 25,962 | n = 25,928 | n = 8,653 | n = 8,629 |
| Age in years, mean (SD) | 30.2 (4.6) | 29.7 (4.9) | 30.2 (4.6) | 30.4 (4.5) | 30.5 (4.4) | 30.2 (4.5) | 29.6 (4.9) |
| <25 | 9,165 (10.6) | 1,293 (15.2) | 965 (11.2) | 2,422 (9.3) | 2,267 (8.7) | 924 (10.7) | 1,294 (15.0) |
| 25–34 | 61,812 (71.6) | 5,818 (68.3) | 6,091 (70.7) | 18 797 (72.4) | 18,844 (72.7) | 6,254 (72.3) | 6,008 (69.6) |
| ≥35 | 15,329 (17.8) | 1,407 (16.5) | 1,560 (18.1) | 4,743 (18.3) | 4,817 (18.6) | 1,475 (17.0) | 1,327 (15.4) |
| Prepregnancy BMI, mean (SD) | 24.1 (4.3) | 24.3 (4.5) | 24.3 (4.4) | 24.2 (4.3) | 24.0 (4.2) | 23.7 (4.1) | 23.9 (4.4) |
| <20 | 10,522 (12.2) | 1,068 (12.5) | 945 (11.0) | 2,954 (11.4) | 3,133 (12.1) | 1,208 (14.0) | 1,214 (14.1) |
| 20–25 | 47,032 (54.5) | 4,307 (50.6) | 4,672 (54.2) | 14 182 (54.6) | 14,388 (55.5) | 4,838 (55.9) | 4,645 (53.8) |
| 25–29.9 | 18,475 (21.4) | 1,936 (22.7) | 1905 (22.1) | 5,671 (21.8) | 5,496 (21.2) | 1,757 (20.3) | 1,710 (19.8) |
| ≥30 | 8,055 (9.3) | 916 (10.8) | 896 (10.4) | 2,500 (9.6) | 2,289 (8.8) | 646 (7.5) | 808 (9.4) |
| Missing data | 2,222 (2.6) | 291 (3.4) | 198 (2.3) | 655 (2.5) | 622 (2.4) | 204 (2.4) | 252 (2.9) |
| Prematurity | 5,391 (6.2) | 567 (6.7) | 551 (6.4) | 1,587 (6.1) | 1,540 (5.9) | 550 (6.4) | 596 (6.9) |
| Missing data | 61 (0.1) | 6 (0.1) | 7 (0.1) | 22 (0.1) | 16 (0.1) | 3 (0.0) | 7 (0.1) |
| Parity | |||||||
| 0 | 39,548 (45.8) | 4,561 (53.5) | 4,196 (48.7) | 11,744 (45.2) | 11,201 (43.2) | 3,858 (44.6) | 3,988 (46.2) |
| 1 | 30,447 (35.3) | 2,667 (31.3) | 2,885 (33.5) | 9,339 (36.0) | 9,561 (36.9) | 3,085 (35.7) | 2,910 (33.7) |
| ≥2 | 16,311 (18.9) | 1,290 (15.1) | 1,535 (17.8) | 4,879 (18.8) | 5,166 (19.9) | 1,710 (19.8) | 1,731 (20.1) |
| Smoking during pregnancy | |||||||
| No | 78,332 (90.8) | 7,570 (88.9) | 7,780 (90.3) | 23,814 (91.7) | 23,769 (91.7) | 7,858 (90.8) | 7,541 (87.4) |
| Occasionally | 1,465 (1.7) | 154 (1.8) | 163 (1.9) | 427 (1.6) | 404 (1.6) | 159 (1.8) | 158 (1.8) |
| Yes | 6,044 (7.0) | 745 (8.7) | 619 (7.2) | 1,586 (6.1) | 1,615 (6.2) | 602 (7.0) | 877 (10.2) |
| Missing data | 465 (0.5) | 49 (0.6) | 54 (0.6) | 135 (0.5) | 140 (0.5) | 34 (0.4) | 53 (0.6) |
| Maternal education | |||||||
| <12 years | 31,116 (36.1) | 3,864 (45.4) | 3,331 (38.7) | 8,858 (34.1) | 8,247 (31.8) | 3,006 (34.7) | 3,810 (44.2) |
| 12–15 years | 34,982 (40.5) | 2,909 (34.2) | 3,408 (39.6) | 10 854 (41.8) | 11,128 (42.9) | 3,537 (40.9) | 3,146 (36.5) |
| ≥16 years | 19,789 (22.9) | 1,672 (19.6) | 1,846 (21.4) | 6,141 (23.7) | 6,442 (24.8) | 2,069 (23.9) | 1,619 (18.8) |
| Missing data | 419 (0.5) | 73 (0.9) | 31 (0.4) | 109 (0.4) | 111 (0.4) | 41 (0.5) | 54 (0.6) |
| Breastfeeding duration, mean (SD) | 9.9 (4.5) | 9.4 (4.6) | 9.6 (4.6) | 9.9 (4.5) | 10.1 (4.5) | 10.2 (4.5) | 9.6 (4.6) |
| <6.0 months | 12,701 (14.7) | 1,424 (16.7) | 1,395 (16.2) | 3,825 (14.7) | 3,525 (13.6) | 1,139 (13.2) | 1,393 (16.1) |
| 6.0–11.9 months | 26,226 (30.4) | 2,453 (28.8) | 2,596 (30.1) | 8,136 (31.3) | 7,969 (30.7) | 2,630 (30.4) | 2,442 (28.3) |
| ≥12 months | 24,304 (28.2) | 1981 (23.3) | 2,270 (26.3) | 7,433 (28.6) | 7,802 (30.1) | 2,580 (29.8) | 2,238 (25.9) |
| Missing data | 23,075 (26.7) | 2,660 (31.2) | 2,355 (27.3) | 6,568 (25.3) | 6,632 (25.6) | 2,304 (26.6) | 2,556 (29.6) |
| Fibre intake (g), mean (SD) | 31.2 (11.9) | 19.4 (8.1) | 23.6 (7.7) | 27.6 (7.1) | 33.1 (7.9) | 38.7 (9.0) | 48.4 (16.7) |
| <20th centile | 15,776 (18.3) | 6,003 (70.5) | 4,016 (46.6) | 4,842 (18.7) | 845 (3.3) | 56 (0.6) | 14 (0.2) |
| 20–40th centile | 16,719 (19.4) | 1,318 (15.5) | 2,431 (28.2) | 8,432 (32.5) | 4,098 (15.8) | 360 (4.2) | 80 (0.9) |
| 40–60th centile | 17,418 (20.2) | 624 (7.3) | 1,209 (14.0) | 6,709 (25.8) | 7,358 (28.4) | 1,235 (14.3) | 283 (3.3) |
| 60–80th centile | 17,931 (20.8) | 325 (3.8) | 633 (7.3) | 4,201 (16.2) | 8,328 (32.1) | 3,099 (35.8) | 1,345 (15.6) |
| 80–100th centile | 18,461 (21.4) | 248 (2.9) | 327 (3.8) | 1,778 (6.8) | 5,299 (20.4) | 3,903 (45.1) | 6,906 (80.0) |
| Missing data | 1 (0.0) | - | - | - | - | - | 1 (0.0) |
| Energy intake (MJ), mean (SD) | 9.8 (3.2) | 6.9 (2.0) | 7.9 (1.8) | 8.9 (1.9) | 10.3 (2.2) | 11.6 (2.5) | 14.1 (5.4) |
| <20th centile | 15,744 (18.2) | 5,699 (66.9) | 3,701 (43.0) | 5,060 (19.5) | 1,205 (4.6) | 70 (0.8) | 9 (0.1) |
| 20–40th centile | 16,886 (19.6) | 1,527 (17.9) | 2,632 (30.5) | 7,694 (29.6) | 4,408 (17.0) | 517 (6.0) | 108 (1.3) |
| 40–60th centile | 17,420 (20.2) | 703 (8.3) | 1,309 (15.2) | 6,636 (25.6) | 6,833 (26.4) | 1,468 (17.0) | 471 (5.5) |
| 60–80th centile | 17,883 (20.7) | 369 (4.3) | 699 (8.1) | 4,541 (17.5) | 7,804 (30.1) | 2,828 (32.7) | 1,642 (19.0) |
| 80–100th centile | 18,372 (21.3) | 220 (2.6) | 275 (3.2) | 2,031 (7.8) | 5,678 (21.9) | 3,770 (43.6) | 6,398 (74.1) |
| Missing data | 1 (0.0) | - | - | - | - | - | 1 (0.0) |
| Offspring characteristics | |||||||
| Cesarean section | 13,001 (15.1) | 1,450 (17.0) | 1,401 (16.3) | 3,863 (14.9) | 3,730 (14.4) | 1,225 (14.2) | 1,332 (15.4) |
| Type 1 diabetes | 346 (0.4) | 23 (0.3) | 45 (0.5) | 102 (0.4) | 99 (0.4) | 42 (0.5) | 35 (0.4) |
| Female | 42,179 (48.9) | 4,189 (49.2) | 4,201 (48.8) | 12,749 (49.1) | 12,715 (49.0) | 4,211 (48.7) | 4,114 (47.7) |
| Birth weight (g), mean (SD) | 3,561 (587) | 3,514 (593) | 3,539 (587) | 3,561 (585) | 3,580 (583) | 3,571 (585) | 3,557 (598) |
| <2,500 | 3,585 (4.2) | 403 (4.7) | 378 (4.4) | 1,108 (4.3) | 965 (3.7) | 341 (3.9) | 390 (4.5) |
| 2,500–3,499 | 33,185 (38.5) | 3,538 (41.5) | 3,401 (39.5) | 9,934 (38.3) | 9,731 (37.5) | 3,267 (37.8) | 3,314 (38.4) |
| 3,500–4,499 | 45,932 (53.2) | 4,261 (50.0) | 4,529 (52.6) | 13,860 (53.4) | 14,067 (54.3) | 4,690 (54.2) | 4,525 (52.4) |
| ≥4,500 | 3,598 (4.2) | 315 (3.7) | 308 (3.6) | 1,058 (4.1) | 1,162 (4.5) | 355 (4.1) | 400 (4.6) |
| Missing data | 6 (0.0) | 1 (0.0) | - | 2 (0.0) | 3 (0.0) | - | - |
| Age at gluten introduction | |||||||
| <4.0 months | 515 (0.6) | 70 (0.8) | 52 (0.6) | 135 (0.5) | 129 (0.5) | 46 (0.5) | 83 (1.0) |
| 4.0–5.9 months | 16,603 (19.2) | 1,575 (18.5) | 1,657 (19.2) | 4,950 (19.1) | 4,974 (19.2) | 1,710 (19.8) | 1,737 (20.1) |
| ≥6 months | 59,347 (68.8) | 5,614 (65.9) | 5,883 (68.3) | 18,193 (70.1) | 18,061 (69.7) | 5,935 (68.6) | 5,661 (65.6) |
| Missing data | 9,841 (11.4) | 1,259 (14.8) | 1,024 (11.9) | 2,684 (10.3) | 2,764 (10.7) | 962 (11.1) | 1,148 (13.3) |
| Coeliac disease diagnosis | 828 (1.0) | 70 (0.8) | 84 (1.0) | 253 (1.0) | 269 (1.0) | 83 (1.0) | 69 (0.8) |
| Missing data | 153 (0.2) | 16 (0.2) | 22 (0.3) | 55 (0.2) | 33 (0.1) | 12 (0.1) | 15 (0.2) |
| Weight gain (kg) 0–12 months, mean (SD) | 6.4 (1.05) | 6.4 (1.07) | 6.4 (1.07) | 6.4 (1.04) | 6.4 (1.05) | 6.3 (1.06) | 6.4 (1.06) |
| Missing data | 28,829 (33.4) | 3,231 (37.9) | 2,923 (33.9) | 8,238 (31.7) | 8,298 (32.0) | 2,911 (33.6) | 3,228 (37.4) |
Abbreviation: BMI, body mass index