Respiratory outcomes at ages 2 and 5 years in groups categorised by maternal smoking during pregnancy and referenced to children whose mothers had never smoked
| Smoking throughout pregnancy | Quit after first trimester | Ex-smoker | Never smoked | |
| OR for diagnosed asthma aged 2 years (95% CI) (n=55)* | 2.09 (0.80 to 5.51), p=0.135 | 3.40 (1.52 to 7.63), p=0.003 | 1.26 (0.57 to 2.80), p=0.566 | 1 |
| OR for recent wheeze aged 2 years (95% CI) (n=179)* | 1.58 (0.89 to 2.79), p=0.017 | 1.53 (0.87 to 2.70), p=0.140 | 1.28 (0.83 to 1.97), p=0.233 | 1 |
| OR for diagnosed asthma aged 5 years (95% CI) (n=116)* | 1.27 (0.63 to 2.56), p=0.507 | 1.26 (0.63 to 2.51), p=0.525 | 0.58 (0.31 to 1.09), p=0.090 | 1 |
| OR for recent wheeze aged 5 years (95% CI) (n=135)* | 1.52 (0.80 to 2.92), p=0.205 | 1.71 (0.91 to 3.20), p=0.095 | 0.86 (0.50 to 1.47), p=0.586 | 1 |
| OR for seeing GP with wheeze aged 5 years (95% CI) (n=97)* | 2.18 (1.08 to 4.43), p=0.030 | 1.78 (0.87 to 3.64), p=0.117 | 0.75 (0.39 to 1.46), p=0.401 | 1 |
| Mean difference in FVC aged 5 years (ml) (n=589)† | −53 (0 to −107), p=0.051 | −12 (+47 to −72), p=0.681 | −15 (+49 to −79), p=0.647 | 0 |
| Mean difference in FEV1 aged 5 years (ml) (n=445)† | −62 (12 to 112), p=0.014 | −18 (+37 to −73), p=0.525 | −57 (+2 to −116), p=0.056 | 0 |
↵* Model adjusted for sex, maternal asthma, current smoke exposure, Scottish Index of Multiple Deprivation, treatment with antibiotics in the first 6 months, breast feeding and maternal intake of vitamin C, D and E.
↵† Model adjusted for sex, height, maternal height, maternal asthma, current smoke exposure and maternal plasma α-tocopherol and cholesterol at enrolment.
FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity.