| Original data | Data after multiple imputation | |
| Maternal characteristics | ||
| Age years | 30.8±4.8 | 30.8±4.8 |
| Gestational age at enrolment weeks | 13.8 (10.1–27.2) | 13.8 (10.1–27.2) |
| Parity | ||
| Nullipara | 2721 (58.5) | 2722 (58.5) |
| Multipara | 1933 (41.5) | 1934 (41.5) |
| Missing | 2 (0.0) | |
| Ethnicity | ||
| European | 3105 (67.1) | 3119 (67.0) |
| Non-European | 1519 (32.9) | 1537 (33.0) |
| Missing | 32 (0.7) | |
| Education | ||
| Primary or secondary | 2161 (47.3) | 2228 (47.9) |
| Higher | 2409 (52.7) | 2428 (52.1) |
| Missing | 86 (1.8) | |
| Stress during pregnancy (global severity index)¶ | 0.13 (0.00–1.25) | 0.16 (0.00–1.17) |
| Smoking during pregnancy | ||
| No | 3824 (86.4) | 4019 (86.3) |
| Yes | 603 (13.6) | 637 (13.7) |
| Missing | 229 (4.9) | |
| History of asthma or atopy | ||
| No | 2567 (61.7) | 2935 (63.0) |
| Yes | 1593 (38.3) | 1721 (37.0) |
| Missing | 496 (10.7) | |
| Pet keeping | ||
| No | 2884 (66.5) | 3101 (66.6) |
| Yes | 1456 (33.5) | 1555 (33.4) |
| Missing | 316 (6.8) | |
| Gestational hypertensive disorders | ||
| No | 4271 (94.0) | 4370 (93.9) |
| Yes | 271 (6.0) | 286 (6.1) |
| Missing | 114 (2.4) | |
| Diabetes gravidarum | ||
| No | 4500 (99.3) | 4611 (99.0) |
| Yes | 33 (0.7) | 45 (0.9) |
| Missing | 123 (2.6) | |
| Pre-pregnancy BMI kg·m−2 | 23.4±4.1 | 23.4±4.1 |
| Pre-pregnancy BMI | ||
| Underweight (<20 kg·m−2) | 727 (15.6) | 727 (15.6) |
| Normal weight (20–24.9 kg·m−2) | 2740 (58.8) | 2740 (58.8) |
| Overweight (25–29.9 kg·m−2) | 844 (18.1) | 844 (18.1) |
| Obese (≥30 kg·m−2) | 345 (7.4) | 345 (7.4) |
| Gestational weight gain kg | 10.4±4.7 | 10.4±4.7 |
| Children’s characteristics | ||
| Female sex | 2326 (50.0) | 2326 (50.0) |
| Gestational age at birth weeks | 40.1 (36.0–42.3) | 40.1 (36.0–42.3) |
| Birthweight g | 3457±546 | 3457±546 |
| Breastfeeding | ||
| No | 339 (7.5) | 352 (7.6) |
| Yes | 4152 (92.5) | 4304 (92.4) |
| Missing | 165 (3.5) | |
| Daycare attendance 1st year | ||
| No | 1693 (44.4) | 2192 (47.1) |
| Yes | 2120 (55.6) | 2464 (52.9) |
| Missing | 843 (18.1) |
Values are presented as mean±sd, n (%) or median (95% range). BMI: body mass index. #: n=4656; ¶: missing information for stress during pregnancy was 14%.