Table 1.
Descriptive maternal, paternal, and offspring characteristics of the six I4C member cohorts included in the pooled dataset
| ALSPAC | CPP | DNBC | JPS | MoBa | TIHS | Total | |
|---|---|---|---|---|---|---|---|
| Recruitment years | 1991–1992 | 1959–1965 | 1996–2002 | 1964–1976 | 1999–2009 | 1987–1995 | 1959–2007 |
| Singleton livebirths with no DS | 13 664 | 50 342 | 8603 | 20 313 | 10 497 | 9 362 | 112 781 |
| Years of follow-up | 14.9 | 5.6 | 11 | 15 | 4.4 | 14.7 | 9.9 |
| Mean (range) | (0.5–15) | (0.0–8.0) | (8.3–14.0) | (15.0–15.0) | (0.5–10.1) | (12.7–15.0) | (0.0–15.0) |
| Maternal age (years) | |||||||
| Mean ± SD | 28.0 ± 5.0 | 24.1 ± 5.9 | 30.5 ± 4.2 | 27.3 ± 5.4 | 30.2 ± 4.6 | 23.6 ± 4.4 | 26.2 ± 5.9 |
| Missing (%) | 0 (0.0) | 0 (0.0) | 2 (0.02) | 77 (3.8) | 10 (0.1) | 0 (0.0) | 89 (0.08) |
| Married or cohabitating, n (%) | 9 588 (70.2)a | 38 658 (76.8) | 8094 (94.1) | 20 142 (99.2) | 9 591 (91.4) | 7 318 (78.2) | 93 389 (82.8) |
| Missing (%) | 861 (6.3) | 2 (0.01) | 359 (4.2) | 114 (0.6) | 591 (5.6) | 32 (0.3) | 1 590 (1.7) |
| Mother completed 12 or more years of education, n (%) | 4 286 (31.4)d | 20 767 (41.3) | 4097 (47.6) | 9 866 (48.6) | 6 246 (59.5) | 1 690 (18.0) | 46 952 (41.6) |
| Missing (%) | 1 536 (11.2) | 122 (0.24) | 2349 (27.3) | 358 (1.8) | 595 (5.7) | 21 (0.2) | 4 981 (4.4) |
| Maternal prenatal smoking, n (%) | 3 530 (25.8) | 23 269 (46.2) | 2 193 (25.5) | 2 568 (12.6) | 925 (8.8) | 5 023 (53.6) | 37 508 (33.3) |
| Missing (%) | 1 639 (12.0) | 263 (0.5) | 9 (0.1) | 193 (1.0) | 2 295 (21.9) | 16 (0.2) | 4 415 (3.9) |
| Passive smoking at home, prenatal, n (%)b | 5 362 (39.2) | n/a | 5584 (64.9) | 7 438 (36.6) | 770 (7.3) | 5 242 (56.0) | 24 396 (39.1) |
| Missing (%) | 1 859 (13.6) | 3005 (34.9) | 3 828 (18.8) | 1 397 (13.3) | 20 (0.2) | 10 109 (16.2) | |
| Parity, n (%) | |||||||
| No prior livebirth | 1 377 (10.1) | 1 142 (2.3) | n/a | n/a | 1 239 (11.8) | n/a | 3 758 (3.6) |
| No prior pregnancy | 4 263 (31.2) | 14 187 (28.2) | 3861 (44.9) | 6 249 (30.8) | 3 229 (30.8) | 31 789 (30.7) | |
| 1–2 | 6 090 (44.6) | 19 768 (39.3) | 4117 (47.9) | 8 713 (42.9) | 4 960 (47.2) | 43 648 (42.2) | |
| ≥3 | 733 (5.4) | 15 191 (30.2) | 261 (3.0) | 5 279 (26.0) | 292 (2.8) | 21 753 (21.0) | |
| Missing (%) | 1 201 (8.8) | 54 (0.1) | 364 (4.2) | 76 (0.4) | 777 (7.4) | 2 472 (2.4) | |
| Maternal pre-pregnancy BMI, kg/m2 | |||||||
| Mean ± SD | 22.9 ± 3.8 | 22.7 ± 4.3 | 23.6 ± 4.4 | 22.1 ± 3.1 | 24.0 ± 4.2 | 23.2 ± 4.8 | 22.9 ± 4.1 |
| Missing (%) | 2 396 (17.5) | 4 372 (8.7) | 493 (5.7) | 6 010 (29.6) | 835 (7.9) | 3 113 (33.2) | 17 219 (15.3) |
| Maternal pregnancy weight gain, kg | |||||||
| Mean ± SD | 12.5 ± 4.7 | 9.8 ± 4.8 | 15.1 ± 5.8 | 11.2 ± 4.3 | 14.9 ± 5.8 | 13.9 ± 6.4 | 11.5 ± 5.4 |
| Missing (%) | 1 573 (11.5) | 3 816 (7.6) | 1947 (22.6) | 5 679 (27.6) | 2 550 (24.3) | 1 704 (18.2) | 17 269 (15.3) |
| Maternal height, cm | |||||||
| Mean ± SD | 163.9 ± 6.7 | 160.9 ± 6.9 | 168.8 ± 6.0 | 162.0 ± 6.0 | 168.0 ± 5.9 | 162.2 ± 7.3 | 162.9 ± 7.2 |
| Missing (%) | 1 717 (12.6) | 3 740 (7.4) | 361 (4.2) | 4 678 (23.0) | 660 (6.3) | 2 452 (26.2) | 13 608 (12.1) |
| Maternal DM, n (%) | n/a | ||||||
| Pre-existing | 442 (3.2)c | 264 (0.5) | 25 (0.3) | 36 (0.2) | 55 (0.5) | 882 (0.8) | |
| Gestational | 55 (0.4) | 127 (0.2) | 139 (1.6) | 110 (0.5) | 85 (0.8) | 516 (0.5) | |
| Missing (%) | 1 585 (11.6) | 129 (0.3) | 0 (0.0) | 90 (0.4) | 0 (0.0) | 1 804 (1.7) | |
| Any previous miscarriage, n (%) | 2 719 (19.9) | 9 031 (17.9) | 1563 (18.2) | 4 416 (21.7) | 1 925 (18.3) | n/a | 19 654 (19.0) |
| Missing (%) | 961 (7.0) | 0 (0) | 365 (4.2) | 104 (0.5) | 777 (7.4) | 2 207 (2.1) | |
| Paternal age (years) | |||||||
| Mean ± SD | 30.7 ± 5.8 | 28.2 ± 7.0 | 32.8 ± 5.1 | 30.9 ± 6.5 | 32.7 ± 5.3 | 26.5 ± 5.6 | 29.8 ± 6.6 |
| Missing (%) | 2 269 (16.6) | 12 795 (25.4) | 123 (1.4) | 654 (3.2) | 47 (0.4) | 215 (2.3) | 16 103 (14.3) |
| Father completed at least 12 years of education, n (%) | 5 151 (37.7)d | 19 209 (38.2) | 2700 (31.4) | 10 828 (53.3) | 4 782 (45.6) | 1 624 (17.3) | 44 294 (39.3) |
| Missing (%) | 2 012 (14.7) | 9 651 (19.2) | 2541 (29.5) | 418 (2.1) | 883 (8.4) | 865 (9.2) | 16 370 (14.5) |
| Gestational age, weeks | |||||||
| Mean ± SD | 39.5 ± 1.9 | 39.4 ± 3.1 | 40.1 ± 1.7 | 39.7 ± 2.2 | 39.5 ± 1.8 | 38.8 ± 2.6 | 39.5 ± 2.6 |
| Missing (%) | 0 (0.0) | 329 (0.6) | 0 (0.0) | 0 (0.0) | 47 (0.4) | 29 (0.3) | 405 (0.4) |
| Gender, male n (%) | 7 052 (51.6) | 25 461 (50.6) | 4367 (50.8) | 10 485 (51.6) | 5 274 (50.2) | 6 673 (71.3) | 59 312 (52.6) |
| Missing (%) | 2 (0.01) | 81 (0.2) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 93 (0.1) |
| Birthweight, grams | |||||||
| Mean ± SD | 3 410 ± 551 | 3 177 ± 531 | 3599 ± 549 | 3 260 ± 508 | 3 604 ± 562 | 3 195 ± 751 | 3 293 ± 577 |
| Missing (%) | 172 (1.3) | 192 (0.4) | 32 (0.4) | 52 (0.3) | 20 (0.2) | 0 (0.0) | 468 (0.4) |
| Placental weight, grams | |||||||
| Mean ± SD | 652 ± 138 | 437 ± 94 | 663 ± 148 | n/a | 676 ± 149 | 613 ± 161 | 531 ± 163 |
| Missing (%) | 8 103 (59.3) | 7 864 (15.6) | 288 (3.3) | 325 (3.1) | 149 (1.6) | 16 729 (18.1) | |
| First born, n (%) | 5 500 (40.2) | 14 187 (28.2) | 3861 (44.9) | 6 248 (30.8) | 4 468 (42.6) | 44 387 (46.9) | 38 651 (34.3) |
| Missing (%) | 1 090 (8.0) | 54 (0.1) | 364 (4.2) | 76 (0.4) | 777 (7.4) | 11 (0.1) | 2 372 (2.1) |
| Length at birth, cm | |||||||
| Mean ± SD | 50.7 ± 2.4 | 49.9 ± 2.7 | 52.3 ± 2.5 | n/a | 50.4 ± 2.4 | 48.8 ± 3.4 | 50.2 ± 2.9 |
| Missing (%) | 3 399 (24.9) | 1 515 (3.0) | 81 (0.9) | 387 (3.7) | 221 (2.4) | 5 603 (6.1) | |
ALSPAC = the Avon Longitudinal Study of Parents and Children (UK); CPP = the Collaborative Perinatal Project (USA); DNBC = the Danish National Birth Cohort (Denmark); DS = Down syndrome; JPS = the Jerusalem Perinatal Study (Israel); MoBa = the Norwegian Mother and Child Cohort Study (Norway); n/a = data not collected/provided; TIHS = the Tasmanian Infant Health Survey (Australia).
a
Concerned marriage only.
b
Passive smoking defined as any exposure to smoke at home by partner or others living in the home.
c
Includes glycosuria.
d
Educational qualifications obtained were used as a proxy – but by law the school leaving age was 16 at the earliest.
Note that if a subject characteristic was n/a for a particular cohort, then the percentage in the ‘Total’ column is based on total number of observations without including that cohort in the summary statistic.