Primary outcomes — descriptive statistics and adjusted relative risks comparing midwives with family physicians and obstetricians (95% confidence intervals)
| Risk score | No. (%) of midwife MRPs | No. (%) of family physician MRPs | No. (%) of obstetrician MRPs | Midwife compared with family physician | Midwife compared with obstetrician | ||
|---|---|---|---|---|---|---|---|
| Numerator/denominator | N | RR (95% CI)* | N | RR (95% CI)* | |||
| Perinatal death | |||||||
| Low risk | 115/46 632 (0.2) | 321/132 309 (0.2) | 403/76 694 (0.5) | 178 941 | 1.046 (0.811–1.350) | 123 326 | 0.482 (0.376–0.618) |
| Moderate risk | 72/15 437 (0.5) | 319/51 519 (0.6) | 531/77 142 (0.7) | 66 956 | 0.789 (0.581–1.071) | 92 579 | 0.675 (0.503–0.906) |
| High risk | 19/1082 (1.8) | 127/5851 (2.2) | 352/18 390 (1.9) | 6933 | 0.863 (0.488–1.525) | 19 472 | 0.941 (0.545–1.624) |
| All | 206/63 151 (0.3) | 767/189 679 (0.4) | 1286/172 226 (0.7) | 252 830 | 0.833 (0.693–1.002) | 235 377 | 0.437 (0.366–0.521) |
| Low birth weight (< 2500 g) | |||||||
| Low risk | 448/46 438 (1.0) | 1967/131 562 (1.5) | 2096/76 299 (2.7) | 178 000 | 0.694 (0.614–0.784) | 122 737 | 0.392 (0.347–0.443) |
| Moderate risk | 498/15 334 (3.2) | 2899/50 866 (5.7) | 5594/76 534 (7.3) | 66 200 | 0.617 (0.552–0.690) | 91 868 | 0.460 (0.414–0.513) |
| High risk | 178/1066 (16.7) | 1348/5693 (23.7) | 5296/18 098 (29.3) | 6759 | 0.755 (0.640–0.890) | 19 164 | 0.609 (0.520–0.713) |
| All | 1124/62 838 (1.8) | 6214/188 121 (3.3) | 12 986/170 931 (7.6) | 250 959 | 0.574 (0.532–0.619) | 233 769 | 0.244 (0.227–0.262) |
| Preterm birth (< 37 wk) | |||||||
| Low risk | 1476/46 005 (3.2) | 5298/130 363 (4.1) | 4297/75 587 (5.7) | 176 368 | 0.823 (0.769–0.881) | 121 592 | 0.593 (0.553–0.636) |
| Moderate risk | 1136/15 168 (7.5) | 5469/50 193 (10.9) | 9435/75 450 (12.5) | 65 361 | 0.720 (0.669–0.774) | 90 618 | 0.607 (0.566–0.651) |
| High risk | 260/1049 (24.8) | 1818/5566 (32.7) | 6889/17 548 (39.3) | 6615 | 0.794 (0.698–0.904) | 18 597 | 0.649 (0.573–0.735) |
| All | 2872/62 222 (4.6) | 12 585/186 122 (6.8) | 20 621/168 585 (12.2) | 248 344 | 0.708 (0.676–0.743) | 230 807 | 0.387 (0.370–0.405) |
| Apgar < 7 at 5 min | |||||||
| Low risk | 756/45 966 (1.6) | 2737/130 326 (2.1) | 1696/75 604 (2.2) | 176 292 | 0.778 (0.707–0.856) | 121 570 | 0.734 (0.663–0.812) |
| Moderate risk | 303/15 157 (2.0) | 1381/50 167 (2.8) | 1868/75 481 (2.5) | 65 324 | 0.735 (0.635–0.851) | 90 638 | 0.763 (0.661–0.881) |
| High risk | 48/1048 (4.6) | 325/5557 (5.8) | 937/17 548 (5.3) | 6605 | 0.781 (0.547–1.115) | 18 596 | 0.791 (0.562–1.113) |
| All | 1107/62 171 (1.8) | 4443/186 050 (2.4) | 4501/168 633 (2.7) | 248 221 | 0.741 (0.686–0.802) | 230 804 | 0.633 (0.586–0.685) |
| Cesarean delivery | |||||||
| Low risk | 3356/46 632 (7.2) | 16 171/132 309 (12.2) | 32 476/76 694 (42.3) | 178 941 | 0.579 (0.555–0.605) | 123 326 | 0.167 (0.160–0.174) |
| Moderate risk | 2396/15 437 (15.5) | 13 328/51 519 (25.9) | 52 907/77 142 (68.6) | 66 956 | 0.593 (0.566–0.622) | 92 579 | 0.228 (0.218–0.239) |
| High risk | 411/1082 (38.0) | 2848/5851 (48.7) | 14 783/18 390 (80.4) | 6933 | 0.779 (0.709–0.855) | 19 472 | 0.492 (0.450–0.538) |
| All | 6163/63 151 (9.8) | 32 347/189 679 (17.1) | 100 166/172 226 (58.2) | 252 830 | 0.564 (0.547–0.582) | 235 377 | 0.169 (0.164–0.175) |
Note: CI = confidence interval, MRP = most responsible provider, RR = relative risk.
↵* Adjusted for parity, maternal residence, history of mental health condition, substance use during pregnancy and antenatal hospital admissions (see Table 2 for definitions). RR > 1.0 denotes a higher risk in midwives; RR < 1.0 denotes a lower risk in midwives.