Table 1.
Descriptive characteristics of inception birth cohort and sample in the current study.
| Characteristic | Inception birth cohort (n = 1074) | Study sample: Random subcohort with 12-month 16S and neurocognitive data (n = 201) |
|---|---|---|
| Sex of child: | ||
| Male | 555 (51·7%) | 106 (52·7%) |
| Female | 519 (48·3%) | 95 (47·3%) |
| Twins (sets) | 10 (1%) | 2 (1%) |
| Maternal country of birth | ||
| Australia | 961 (89·5%) | 179 (89·1%) |
| Other | 110 (10·2%) | 21 (10·4%) |
| Unknown | 3 (0·3%) | 1 (0·5%) |
| Paternal country of birth | ||
| Australia | 915 (85·2%) | 169 (84·1%) |
| Other | 108 (10·1%) | 19 (9·4%) |
| Unknown | 51 (4·8%) | 13 (6·5%) |
| Maternal age, years (mean & SD) | 31.3 (4·8) | 32.4 (4·2) |
| Paternal age, years (mean & SD) | 33.5 (5·9) | 34.2 (5·1) |
| Maternal education | ||
| < year 10 of high school | 12 (1·1%) | 2 (1·0%) |
| Year 10 of high school | 80 (7·5%) | 14 (7·0%) |
| Year 12 of high school | 162 (15·1%) | 28 (13·9%) |
| Trade, certificate, diploma | 266 (24·8%) | 39 (19·4%) |
| Bachelor degree | 354 (33%) | 76 (37·8%) |
| Postgraduate degree | 194 (18·1%) | 42 (20·1%) |
| Unknown | 6 (6%) | 0 (0·0%) |
| SEIFA | ||
| Low | 357 (33·2%) | 59 (29·4%) |
| Middle | 353 (32·9%) | 73 (36·3%) |
| High | 351 (32·7%) | 69 (34·3%) |
| Unknown | 13 (1·9%) | 0 (0·0%) |
| Number of siblings including twins | ||
| 0 | 473 (44·0%) | 77 (36·3%) |
| 1 | 383 (35·7%) | 87 (44·8%) |
| 2 | 177 (16·5%) | 32 (16·4%) |
| 3 or more | 41 (3·8%) | 5 (2·5%) |
| Maternal cigarette smoking in pregnancy: | ||
| Yes | 169 (15·7%) | 19 (9·5%) |
| No | 892 (83·1%) | 182 (90·5%) |
| Unknown | 13 (1·2%) | 0 (0·0%) |
| Pet ownership | ||
| Yes | 790 (73·6%) | 143 (71·1%) |
| No | 278 (25·9%) | 58 (28·9%) |
| Unknown | 6 (0·6%) | 0 (0%) |
| Livestock ownership | ||
| Yes | 73 (6·8%) | 10 (5·0%) |
| No | 985 (91·7%) | 188 (93·5%) |
| Unknown | 16 (1·5%) | 3 (1·5%) |
| Delivered in a government hospital | ||
| Yes | 780 (72·6%) | 121 (60·2%) |
| No | 294 (27·4%) | 80 (39·8%) |
| Delivery via Caesarean section | 333 (31%) | 70 (34·9%) |
| Gestational age at birth: | ||
| 32 to 36 completed weeks | 47 (4·4%) | 4 (2%) |
| 37 to 42 completed weeks | 1027 (95·6%) | 197 (98%) |
| > 42 completed weeks | 0 (0·0%) | 0 (0·0%) |
| Birth weight in grams (mean & SD) | 3528 (519) | 3522 (522) |
| Internalising subscale t score (mean & IQR) | 41 (14) | 41 (14) |
| Externalising subscale t score (mean & IQR) | 44 (12) | 46 (13) |
| Total problems subscale t score (mean & IQR) | 43 (13) | 44 (13) |