Table 2.
Differences in potential confounding factors between individuals in ARIES whose mothers did not smoke in pregnancy compared with sustained smokers
| Non-smoker (N = 699)a | Sustained (N = 91)a | P-value for difference | |
|---|---|---|---|
| Sex | |||
| Male | 49.4 | 47.3 | 0.71 |
| Female | 50.6 | 52.8 | |
| Maternal age (years) | 30.5 (4.1) | 27.9 (5.4) | <0.001 |
| Maternal age (categories) | |||
| <25 | 7.6 | 30.8 | <0.001 |
| 25–30 | 39.2 | 37.4 | |
| >30 | 53.2 | 31.9 | |
| Parity | |||
| 0 | 45.5 | 51.1 | 0.53 |
| 1 | 37.7 | 32.2 | |
| 2 | 13.2 | 11.1 | |
| 3+ | 3.6 | 5.6 | |
| Maternal education | |||
| CSE/vocational | 13.9 | 33.0 | <0.001 |
| O-level | 32.7 | 40.9 | |
| A-level | 30.4 | 18.2 | |
| Degree | 23.1 | 8.0 | |
| Social class | |||
| I | 22.9 | 4.9 | <0.001 |
| II | 44.0 | 39.0 | |
| III (NM) | 24.4 | 20.7 | |
| III (M) | 5.3 | 22.0 | |
| IV or V | 3.5 | 13.4 | |
| Maternal BMI | 22.8 (3.7) | 23.0 (3.6) | 0.63 |
| Maternal BMI (categories) | |||
| <18.5 | 3.3 | 3.5 | 0.59 |
| 18.5–25 | 79.1 | 76.5 | |
| 25–30 | 13.1 | 14.1 | |
| 30+ | 4.6 | 5.9 | |
| Maternal weight | 61.6 (10.4) | 61.5 (10.5) | 0.95 |
| Alcohol | |||
| Non-drinker | 34.2 | 40.9 | 0.040 |
| Drank before 18 weeks of gestation | 15.6 | 5.7 | |
| Still drinking at 18 weeks of gestation | 50.2 | 53.4 | |
| Paternal smoking | |||
| Non-smoker | 78.6 | 20.9 | <0.001 |
| Smoker | 21.4 | 79.1 | |
aN varies according to completeness of data on baseline characteristics.