Outcome | Spontaneous delivery | Attempted forceps delivery | Attempted vacuum delivery | Attempted forceps v. attempted vacuum† | ||||||
---|---|---|---|---|---|---|---|---|---|---|
n | Rate* | n | Rate* | n | Rate* | ARR | 95% CI | NNT‡ | 95% CI | |
All deliveries | 938 664 | 38 500 | 110 987 | |||||||
Maternal trauma | 32 366 | 3.45 | 9728 | 25.27 | 14 614 | 13.17 | 1.70 | 1.65 to 1.75 | 11 | 10 to 12 |
Obstetric anal sphincter injury | 26 238 | 2.80 | 8285 | 21.52 | 12 948 | 11.67 | 1.66 | 1.61 to 1.70 | 13 | 12 to 14 |
Third-degree perineal tear | 24 015 | 2.56 | 7346 | 19.08 | 11 457 | 10.32 | 1.64 | 1.59 to 1.69 | 15 | 14 to 16 |
Fourth-degree perineal tear | 2069 | 0.22 | 848 | 2.20 | 1354 | 1.22 | 1.78 | 1.62 to 1.97 | 103 | 83 to 129 |
Unspecified third- or fourth-degree tear | 154 | 0.02 | 93 | 0.24 | 140 | 0.13 | 1.98 | 1.46 to 2.68 | 785 | 458 to 1672 |
Cervical tear | 1753 | 0.19 | 208 | 0.54 | 388 | 0.35 | 1.33 | 1.08 to 1.63 | 918 | 481 to 3788 |
High vaginal laceration | 1863 | 0.20 | 1193 | 3.10 | 1036 | 0.93 | 2.51 | 2.28 to 2.75 | 71 | 61 to 83 |
Other pelvic trauma | 2986 | 0.32 | 454 | 1.18 | 615 | 0.55 | 1.94 | 1.66 to 2.27 | 231 | 171 to 329 |
Repair of urethra or bladder | 300 | 0.03 | 20 | 0.05 | 45 | 0.04 | 1.24§ | 0.69 to 2.22 | – | – |
All live births* | 880 532 | 35 663 | 103 000 | – | – | – | – | |||
Neonatal trauma | 1657 | 1.88 | 341 | 9.56 | 987 | 9.58 | 0.94 | 0.82 to 1.09 | – | – |
Intracranial hemorrhage | 25 | 0.03 | 25 | 0.70 | 85 | 0.83 | 0.76 | 0.44 to 1.33 | – | – |
Skull fracture | 6 | 0.01 | 24 | 0.67 | 27 | 0.26 | 2.41§ | 1.29 to 4.49 | 3224 | 1302 to 15 674 |
Subgaleal hemorrhage | 31 | 0.04 | 33 | 0.92 | 254 | 2.47 | 0.28 | 0.19 to 0.42 | −652 | −810 to −580 |
Central nervous system injury | 44 | 0.05 | 41 | 1.15 | 276 | 2.68 | 0.33 | 0.23 to 0.48 | −643 | −829 to −560 |
Peripheral nervous system injury | 837 | 0.95 | 173 | 4.85 | 351 | 3.41 | 1.33 | 1.08 to 1.65 | 873 | 443 to 3602 |
Erb paralysis | 323 | 0.37 | 71 | 1.99 | 120 | 1.17 | 1.80 | 1.27 to 2.55 | 1050 | 542 to 3112 |
Other brachial plexus injury | 516 | 0.59 | 107 | 3.00 | 237 | 2.30 | 1.15 | 0.88 to 1.50 | – | – |
Injury to the long bones | 228 | 0.26 | 22 | 0.62 | 108 | 1.05 | 0.77 | 0.46 to 1.28 | – | – |
Seizures | 520 | 0.59 | 73 | 2.05 | 170 | 1.65 | 1.32 | 0.94 to 1.84 | – | – |
Neonatal death | 41 | 0.05 | 11 | 0.31 | 31 | 0.30 | 1.10§ | 0.51 to 2.37 | – | – |
Note: ARR = adjusted rate ratio, CI = confidence interval, NNT = number needed to treat.
↵* Rates of maternal trauma are per 100 deliveries. Rates of neonatal trauma are per 1000 live births. Infants with congenital anomalies excluded.
↵† Adjusted models include maternal age, parity, maternal hypertension, maternal diabetes, fetal distress, post-term delivery, pelvic station of presenting part, macrosomic infant and province or territory of maternal residence.
↵‡ The NNT is the mean number of deliveries that need to be delivered by vacuum rather than forceps to avoid 1 case of the outcome of interest. Negative NNT values represent the number of deliveries that need to be delivered by forceps rather than vacuum to avoid 1 case of the outcome of interest. We calculated adjusted NNTs as the inverse of the adjusted rate difference, which we derived from baseline trauma rates and adjusted rate ratios.
↵§ Adjusted model did not converge given the small number of observations. Unadjusted estimates provided.