Change in obstetric trauma and severe birth trauma rates per 1% absolute increase in operative vaginal delivery rates and associated number of excess cases per year*
| Outcome | Nulliparous | Parous | ||||
|---|---|---|---|---|---|---|
| No previous cesarean | With a previous cesarean | |||||
| ARR (95% CI) | No. of excess cases/yr† | ARR (95% CI) | No. of excess cases/yr† | ARR (95% CI) | No. of excess cases/yr† | |
| Obstetric trauma | ||||||
| All OVD | 1.06 (1.05–1.06) | 708 | 1.10 (1.08–1.13) | 360 | 1.11 (1.07–1.16) | 158 |
| Operative instrument | ||||||
| Forceps | 1.09 (1.08–1.10) | 1061 | 1.26 (1.10–1.43) | 937 | 1.11 (1.00–1.25) | 158 |
| Vacuum | 1.06 (1.05–1.07) | 708 | 1.05 (1.03–1.08) | 180 | 1.16 (1.11–1.22) | 230 |
| Sequential | 1.44 (1.35–1.55) | 5189 | 1.19 (0.84–1.67) | – | 0.95 (0.83–1.09) | – |
| Pelvic station | ||||||
| Outlet | 1.07 (1.06–1.09) | 825 | 1.22 (1.14–1.30) | 793 | 1.17 (1.04–1.31) | 245 |
| Low | 1.04 (1.03–1.05) | 472 | 0.98 (0.93–1.03) | – | 1.02 (0.94–1.11) | – |
| Midpelvic | 1.07 (1.07–1.08) | 825 | 1.14 (1.12–1.17) | 504 | 1.25 (1.20–1.30) | 360 |
| Severe birth trauma | ||||||
| All OVD | 1.05 (1.03–1.07) | 18 | 0.98 (0.94–1.04) | – | 1.02 (0.85–1.22) | – |
| Operative instrument | ||||||
| Forceps | 1.01 (0.95–1.08) | – | 1.09 (0.68–1.76) | – | 0.86 (0.37–2.00) | – |
| Vacuum | 0.97 (0.90–1.04) | – | 0.96 (0.89–1.04) | – | 1.25 (0.91–1.72) | – |
| Sequential | 1.53 (1.03–2.27) | 191 | 2.00 (0.58–6.86) | – | 0.47 (0.17–1.27) | – |
| Pelvic station | ||||||
| Outlet | 1.03 (0.96–1.10) | – | 0.91 (0.71–1.15) | – | 1.27 (0.58–2.80) | – |
| Low | 1.06 (1.01–1.12) | 22 | 1.18 (0.98–1.43) | – | 0.87 (0.49–1.55) | – |
| Midpelvic | 1.04 (1.01–1.07) | 14 | 0.94 (0.87–1.02) | – | 1.12 (0.82–1.53) | – |
Note: ARR = adjusted rate ratio, CI = confidence interval, OVD = operative vaginal delivery.
↵* ARRs and 95% CIs expressing the change in obstetric trauma and severe birth trauma rates per 1% absolute increase in OVD rates and associated number of excess cases per year, term singleton deliveries, Canada, 2004–2014; includes data from Alberta, Manitoba, Ontario, and Saskatchewan. Crude and adjusted rate ratios were obtained from ecological random-intercept Poisson regression models. Adjusted for rates of older maternal age (≥ 35 years of age), hypertension, diabetes, labour induction, macrosomia (> 4000 g), and year of delivery.
↵† Number of excess cases of obstetric trauma and severe birth trauma in Canada annually, based on the number of births in Canada in 2015/16.13