Secondary 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)* | |||
| Labour induction with oxytocin | |||||||
| Low risk | 2986/46 632 (6.4) | 13 859/132 309 (10.5) | 10 758/76 694 (14.0) | 178 941 | 0.609 (0.582–0.638) | 123 326 | 0.474 (0.452–0.497) |
| Moderate risk | 1898/15 437 (12.3) | 8559/51 519 (16.6) | 9411/77 142 (12.2) | 66 956 | 0.741 (0.701–0.783) | 92 579 | 0.994 (0.941–1.051) |
| High risk | 198/1082 (18.3) | 1089/5851 (18.6) | 1541/18 390 (8.4) | 6933 | 0.972 (0.827–1.142) | 19 472 | 2.202 (1.878–2.581) |
| All | 5082/63 151 (8.0) | 23 507/189 679 (12.4) | 21 710/172 226 (12.6) | 252 830 | 0.644 (0.622–0.667) | 235 377 | 0.622 (0.600–0.644) |
| Assisted vaginal delivery (vacuum, forceps or both) | |||||||
| Low risk | 2600/46 632 (5.6) | 15 985/132 309 (12.1) | 11 316/76 694 (14.8) | 178 941 | 0.463 (0.440–0.486) | 123 326 | 0.408 (0.388–0.430) |
| Moderate risk | 788/15 437 (5.1) | 5106/51 519 (9.9) | 5482/77 142 (7.1) | 66 956 | 0.520 (0.476–0.568) | 92 579 | 0.732 (0.670–0.800) |
| High risk | 51/1082 (4.7) | 393/5851 (6.7) | 884/18 390 (4.8) | 6933 | 0.676 (0.476–0.959) | 19 472 | 1.031 (0.734–1.448) |
| All | 3439/63 151 (5.4) | 21 484/189 679 (11.3) | 17 682/172 226 (10.3) | 252 830 | 0.477 (0.457–0.498) | 235 377 | 0.524 (0.501–0.547) |
| Spontaneous vaginal birth | |||||||
| Low risk | 40 676/46 632 (87.2) | 100 153/132 309 (75.7) | 32 902/76 694 (42.9) | 178 941 | 1.135 (1.129–1.141) | 123 326 | 1.919 (1.892–1.945) |
| Moderate risk | 12 253/15 437 (79.4) | 33 085/51 519 (64.2) | 18 753/77 142 (24.3) | 66 956 | 1.265 (1.248–1.282) | 92 579 | 3.846 (3.758–3.936) |
| High risk | 620/1082 (57.3) | 2610/5851 (44.6) | 2723/18 390 (14.8) | 6933 | 1.366 (1.259–1.481) | 19 472 | 4.529 (4.163–4.927) |
| All | 53 549/63 151 (84.8) | 135 848/189 679 (71.6) | 54 378/172 226 (31.6) | 252 830 | 1.189 (1.182–1.196) | 235 377 | 2.882 (2.838–2.926) |
| VBAC† | |||||||
| Low risk | 864/1013 (85.3) | 1183/1506 (78.6) | 669/1299 (51.5) | 2519 | 1.101 (1.049–1.155) | 2312 | 1.716 (1.575–1.869) |
| Moderate risk | 1943/2353 (82.6) | 3659/4659 (78.5) | 2447/4545 (53.8) | 7012 | 1.063 (1.030–1.096) | 6898 | 1.584 (1.499–1.674) |
| High risk | 167/213 (78.4) | 525/685 (76.6) | 524/901 (58.2) | 898 | 1.027 (0.928–1.137) | 1114 | 1.388 (1.238–1.557) |
| All | 2974/3579 (83.1) | 5367/6850 (78.4) | 3640/6745 (54.0) | 10 429 | 1.072 (1.045–1.099) | 10 324 | 1.590 (1.513–1.671) |
| Third- or fourth-degree perineal tears‡ | |||||||
| Low risk | 1674/28 554 (5.9) | 4708/77 367 (6.1) | 2941/31 814 (9.2) | 105 921 | 0.964 (0.901–1.031) | 60 368 | 0.650 (0.605–0.699) |
| Moderate risk | 545/8551 (6.4) | 1470/24 877 (5.9) | 1263/16 755 (7.5) | 33 428 | 1.107 (0.984–1.245) | 25 306 | 0.910 (0.807–1.026) |
| High risk | 22/407 (5.4) | 85/1705 (5.0) | 153/2219 (6.9) | 2112 | 1.136 (0.651–1.982) | 2626 | 0.936 (0.550–1.593) |
| All | 2241/37 512 (6.0) | 6263/103 949 (6.0) | 4357/50 788 (8.6) | 141 461 | 0.993 (0.937–1.053) | 88 300 | 0.703 (0.661–0.747) |
| Breast- or chest-feeding initiation at birth | |||||||
| Low risk | 30 137/46 545 (64.7) | 75 160/131 746 (57.0) | 34 509/76 461 (45.1) | 178 291 | 1.134 (1.122–1.146) | 123 006 | 1.429 (1.409–1.448) |
| Moderate risk | 9822/15 350 (64.0) | 26 003/50 989 (51.0) | 30 397/76 744 (39.6) | 66 339 | 1.267 (1.243–1.291) | 92 094 | 1.664 (1.632–1.697) |
| High risk | 567/1057 (53.6) | 2117/5704 (37.1) | 4969/18 207 (27.3) | 6761 | 1.464 (1.345–1.594) | 19 264 | 2.000 (1.848–2.165) |
| All | 40 526/62 952 (64.4) | 103 280/188 439 (54.8) | 69 875/171 412 (40.8) | 251 391 | 1.180 (1.169–1.191) | 234 364 | 1.618 (1.599–1.637) |
Note: CI = confidence interval, MRP = most responsible provider, RR = relative risk, VBAC = vaginal birth after cesarean.
↵* Adjusted for parity, maternal residence, history of mental health condition, substance use during pregnancy, and antenatal hospital admissions (see Table 2).
↵† Denominator includes people with a previous cesarean scar who were identified as eligible for VBAC or eligibility is unknown or not documented, and current delivery was singleton, vertex presentation. Denominator excludes people with a delivery episode and a history of cesarean who were not eligible for VBAC per the chart or people with a previous scar and unknown or not documented VBAC eligibility who did not have a singleton vertex pregnancy.
↵‡ Analysis is restricted to those with a vaginal birth.