Subgroup analysis of the effect of active tobacco use during pregnancy on wheezing occurrence in infants
| Variable | Groups | OR (95% CI) | I2 (%) | X2 p value |
| Sample size | <1000 | 1.92 (1.31 to 2.85) | 0.0 | 0.72 |
| ≥1000 | 1.43 (1.19 to 1.73) | 70.4 | 0.01 | |
| Study design | Prospective cohort | 1.72 (1.25 to 2.37) | 74 | 0.00 |
| Retrospective cohort | 1.36 (1.20 to 1.55) | 0.0 | 0.58 | |
| Methodological quality | Moderate | 1.29 (1.10 to 1.51) | 29.3 | 0.23 |
| High | 1.77 (1.35 to 2.31) | 52.9 | 0.08 |