Characteristics of the total study population, by maternal qualifications
| Total | Degree plus | Diploma | A-levels | GCSE grades A–C | GCSE grades D–G | None | p-value# | |
| Subjects n (%) | 11 141 (100) | 1088 (17.8) | 1165 (9.4) | 1165 (9.8) | 3861 (36.1) | 1145 (11.2) | 1722 (15.7) | |
| Wheeze phenotype | ||||||||
| Never | 66.0 | 69.8 | 69.3 | 71.7 | 65.2 | 63.3 | 59.7 | <0.001 |
| Early remitting | 17.1 | 15.7 | 14.2 | 13.1 | 17.6 | 19.6 | 19.9 | |
| Persistent/relapsing | 12.0 | 11.5 | 11.6 | 11.0 | 12.1 | 12.9 | 12.9 | |
| Transient/intermittent | 4.9 | 3.0 | 4.8 | 4.2 | 5.1 | 4.3 | 7.5 | |
| Female | 49.1 | 49.9 | 47.3 | 49.8 | 48.4 | 48.6 | 48.6 | 0.95 |
| Child's ethnicity | ||||||||
| White | 88.0 | 88.9 | 90.5 | 89.7 | 92.2 | 91.4 | 72.5 | <0.001 |
| Mixed | 3.0 | 3.7 | 2.8 | 2.7 | 2.6 | 2.7 | 3.7 | |
| Indian | 1.7 | 2.4 | 1.4 | 2.4 | 0.9 | 1.2 | 2.7 | |
| Pakistani and Bangladeshi | 3.8 | 1.2 | 1.2 | 3.0 | 2.3 | 2.6 | 13.1 | |
| Black or black British | 2.5 | 2.5 | 3.4 | 1.3 | 1.6 | 1.9 | 5.3 | |
| Other | 1.0 | 1.3 | 0.7 | 0.9 | 0.5 | 0.2 | 2.7 | |
| Maternal age years | ||||||||
| 14–19 | 7.5 | 0 | 0.5 | 3.9 | 8.0 | 16.7 | 14.8 | <0.001 |
| 20–24 | 16.7 | 2.8 | 9.2 | 15.1 | 19.1 | 25.9 | 26.0 | |
| 25–29 | 28.6 | 25.4 | 33.7 | 30.6 | 28.6 | 31.0 | 25.9 | |
| 30–34 | 30.3 | 42.7 | 37.2 | 32.6 | 29.3 | 18.8 | 21.2 | |
| 35–39 | 14.8 | 25.6 | 17.5 | 14.7 | 13.2 | 7.1 | 10.3 | |
| ≥40 | 2.1 | 3.5 | 1.9 | 3.1 | 1.8 | 0.6 | 1.8 | |
| Maternal atopy | ||||||||
| None | 73.0 | 69.4 | 70.6 | 69.3 | 68.6 | 71.6 | 70.4 | 0.18 |
| Asthma or eczema | 23.4 | 21.4 | 25.0 | 21.6 | 24.6 | 23.9 | 22.4 | |
| Asthma and eczema | 6.5 | 5.9 | 5.4 | 7.4 | 6.5 | 7.2 | 6.3 | |
| Maternal BMI | ||||||||
| Underweight | 5.5 | 3.1 | 3.0 | 3.4 | 5.3 | 8.4 | 9.9 | <0.001 |
| Normal range | 65.7 | 75.5 | 68.0 | 66.7 | 63.5 | 61.7 | 59.7 | |
| Overweight | 20.1 | 15.5 | 20.6 | 20.5 | 21.3 | 19.5 | 22.5 | |
| Obese | 6.3 | 5.0 | 5.9 | 6.3 | 7.3 | 7.2 | 5.4 | |
| Morbidly obese | 2.4 | 0.9 | 2.6 | 3.0 | 2.6 | 3.2 | 2.5 | |
| Maternal smoking | ||||||||
| Never | 65.2 | 87.8 | 77.6 | 76.0 | 60.3 | 47.7 | 48.8 | <0.001 |
| Smoked before pregnancy | 14.7 | 9.4 | 14.6 | 14.2 | 18.4 | 17.2 | 10.5 | |
| Smoked during pregnancy | 20.2 | 2.8 | 7.8 | 9.8 | 21.2 | 35.0 | 40.7 | |
| Low birthweight | 6.2 | 3.6 | 5.3 | 5.3 | 6.2 | 6.4 | 10.0 | <0.001 |
| Caesarean section | 20.5 | 24.8 | 24.1 | 19.1 | 20.1 | 18.4 | 16.9 | <0.001 |
| Preterm <37 weeks gestation | 5.8 | 4.7 | 5.4 | 3.9 | 6.5 | 5.3 | 7.1 | 0.008 |
| Breastfeeding | ||||||||
| Never | 31.5 | 7.1 | 18.6 | 19.7 | 35.8 | 47.3 | 52.8 | <0.001 |
| ≤1 week | 12.1 | 8.1 | 13.0 | 11.0 | 12.6 | 16.5 | 12.1 | |
| 1–6 weeks | 13.1 | 10.0 | 13.9 | 14.0 | 15.4 | 13.2 | 10.7 | |
| 6 weeks–6 months | 19.8 | 26.9 | 24.9 | 24.9 | 19.1 | 13.2 | 11.7 | |
| ≥6 months | 23.6 | 47.9 | 29.7 | 30.5 | 17.0 | 9.8 | 12.7 | |
| Exposure to smoke in same room | 13.1 | 2.9 | 4.4 | 6.8 | 13.2 | 23.0 | 26.2 | <0.001 |
| Damp exposure | 13.5 | 9.8 | 9.7 | 11.4 | 13.0 | 16.0 | 20.6 | <0.001 |
| “Grime” in the environment | 21.1 | 20.8 | 18.9 | 19.3 | 20.2 | 20.6 | 26.3 | 0.004 |
| Furry pets | 37.5 | 29.8 | 38.5 | 33.0 | 41.5 | 42.0 | 35.9 | <0.001 |
| Siblings in household n | ||||||||
| 1 | 49.5 | 44.6 | 45.1 | 41.5 | 45.8 | 31.6 | 42.2 | |
| 2/3 | 51.1 | 47.2 | 51.9 | 51.3 | 53.1 | 48.6 | 51.8 | <0.001 |
| ≥4 | 6.9 | 3.3 | 3.3 | 3.8 | 6.2 | 6.4 | 17.2 | |
| Childcare | ||||||||
| None | 68.2 | 49.0 | 59.1 | 60.5 | 70.9 | 76.8 | 87.9 | <0.001 |
| Informal | 18.0 | 14.6 | 21.6 | 22.5 | 20.6 | 18.2 | 10.9 | |
| Formal | 13.8 | 36.4 | 19.2 | 17.0 | 8.5 | 5.0 | 1.2 |
Data are presented as %, unless otherwise stated. All percentages are adjusted for sampling design and attrition. Item missingness: ethnicity 23, maternal age 7, maternal atopy 17, maternal body mass index (BMI) 657, maternal smoking 36, preterm birth 155, Caesarean section 9, environmental tobacco smoke exposure 1, damp exposure 16, grime exposure 103, furry pet exposure 1, childcare type 42. GCSE: General Certificate of Secondary Education. #: Chi-squared.