Risk of current asthma in overweight and obese women by years of hormonal contraceptive (HC) use
| Duration of HC use | OR# (95% CI) | p-value |
| Nil | 0.83 (0.54–1.29) | 0.413 |
| 5 years | 1.01 (0.74–1.39) | 0.932 |
| 10 years | 1.23 (0.97–1.57) | 0.093 |
| 15 years | 1.50 (1.15–1.95) | 0.003 |
| 20 years | 1.82 (1.27–2.61) | 0.001 |
| 25 years | 2.21 (1.35–3.61) | 0.001 |
| 30 years | 2.69 (1.43–5.05) | 0.002 |
#: adjusted for maternal atopy, current smoking status and social class.