Before | During | After | ||
Non-intervention area | Births | 212 445 | 121 991 | 264 109 |
Surgery | 277 | 144 | 348 | |
Risk of surgery per 1000 live births | 1.31 (1.16 to 1.46) | 1.19 (1.00 to 1.39) | 1.32 (1.18 to 1.46) | |
Relative risk | 1 | 0.91 (0.74 to 1.11) | 1.01 (0.86 to 1.18) | |
Intervention area | Births | 61 314 | 36 129 | 81 387 |
Surgery | 69 | 37 | 43 | |
Risk of surgery per 1000 live births | 1.13 (0.88 to 1.42) | 1.04 (0.73 to 1.40) | 0.54 (0.39 to 0.70) | |
Relative risk | 1 | 0.91 (0.60 to 1.35) | 0.47 (0.32 to 0.68) | |
Difference | Relative risk interaction | – | 1.01 (0.64 to 1.56) | 0.46 (0.31 to 0.70) |
Data shown are counts for births and surgery, risks per 1000 live births and relative risks and interaction relative risks derived from logistic regression models (assuming that, since the event rate is very low, the ORs are estimates of the relative risks, ie, risk ratios) with the main effects and an area/period interaction. Numbers in parentheses are 95% CIs.