Table 3 Effect estimates and certainty of evidence for clinical interventions that influence VBAC rates
Comparison | Study design (no. of studies) | Vaginal delivery – assisted vs. unassisted | Comparison 1 (no. of women with VBAC/no. of women) | Comparison 2 (no. of women with VBAC/no. of women) | Risk Ratio, M-H, Random (95% CI) | I2 (%) | Certainty of Evidence |
|---|---|---|---|---|---|---|---|
Pharmacologic induction | |||||||
 PGE1 vs. spontaneous labor | Prospective cohort (3) |  | 150/206 | 343/453 | 1.08 (0.67, 1.75) | 92 | Very Low |
| Â | Retrospective cohort (1) | Â | 21/30 | 156/167 | 0.75 (0.59, 0.95) | NA | Very Low |
 PGE2 vs. spontaneous labor | RCT (1) |  | 82/143 | 83/151 | 1.04 (0.85, 1.28) | NA | Low |
| Â | Â | Assisted | 12/143 | 9/151 | 1.41 (0.61, 3.24) | NA | Low |
| Â | Â | Unassisted | 70/143 | 74/151 | 1.00 (0.79, 1.26) | NA | Low |
| Â | Prospective cohort (4) | Â | 215/314 | 820/1253 | 0.98 (0.87, 1.10) | 32 | Very Low |
| Â | Â | Assisted | 4/97 | 60/931 | 0.64 (0.24, 1.72) | NA | Very Low |
| Â | Â | Unassisted | 58/97 | 524/931 | 1.06 (0.89, 1.26) | NA | Very Low |
| Â | Retrospective cohort (1) | Â | 37/54 | 3111/4263 | 0.94 (0.78, 1.13) | NA | Very Low |
 Oxytocin vs. spontaneous labor/no oxytocin | Prospective cohort (2) |  | 509/774 | 1400/1734 | 0.80 (0.76, 0.85) | 0 | Very Low |
| Â | Retrospective cohort (6) | Â | 539/771 | 3785/5090 | 0.88 (0.72, 1.07) | 91 | Very Low |
 PGE1 + oxytocin vs. spontaneous labor | Retrospective cohort (1) |  | 73/113 | 156/167 | 0.69 (0.60, 0.80) | NA | Very Low |
Mifepristone vs. placebo | RCT (1) | Â | 11/16 | 8/16 | 1.38 (0.76, 2.48) | NA | Very Low |
| Â | Â | Assisted | 5/16 | 4/16 | 1.25 (0.41, 3.82) | NA | Very Low |
| Â | Â | Unassisted | 6/16 | 4/16 | 1.50 (0.52, 4.32) | NA | Very Low |
 Epidural analgesia vs. no epidural | Retrospective cohort (1) |  | 77/87 | 125/150 | 1.06 (0.96, 1.18) | NA | Very Low |
 Oxytocin (induction) vs. oxytocin (augmentation) | Prospective cohort (1) |  | 23/32 | 177/257 | 1.04 (0.83, 1.32) | NA | Very Low |
| Â | Retrospective cohort (1) | Â | 28/48 | 22/25 | 0.66 (0.50, 0.88) | NA | Very Low |
 Active inpatient management (+/− oxytocin) vs. expectant outpatient management (+/− oxytocin) | RCT (1) |  | 80/95 | 77/93 | 1.02 (0.90, 1.15) | NA | Very Low |
| Â | Â | Assisted | 17/95 | 19/93 | 0.88 (0.49, 1.58) | NA | Very Low |
| Â | Â | Unassisted | 63/95 | 58/93 | 1.06 (0.86, 1.32) | NA | Very Low |
 Oxytocin vs. PGE1 | Retrospective cohort (1) |  | 52/83 | 21/30 | 0.90 (0.67, 1.19) | NA | Very Low |
 Oxytocin vs. PGE2 | RCT (1) |  | 15/21 | 17/21 | 0.88 (0.63, 1.24) | NA | Very Low |
| Â | Â | Assisted | 4/21 | 5/21 | 0.80 (0.25, 2.57) | NA | Very Low |
| Â | Â | Unassisted | 11/21 | 12/21 | 0.92 (0.53, 1.59) | NA | Very Low |
| Â | Prospective cohort (1) | Â | 135/208 | 105/146 | 0.90 (0.78, 1.04) | NA | Very Low |
| Â | Retrospective cohort (1) | Â | 183/254 | 37/54 | 1.05 (0.86, 1.28) | NA | Very Low |
 PGE2 vs. no PGE2 | Prospective cohort (1) |  | 233/453 | 3513/4569 | 0.67 (0.61, 0.73) | NA | Very Low |
 Induction (oxytocin, misoprostol + oxytocin augmentation, PGE2) vs. spontaneous labor | Retrospective cohort (1) |  | 33/57 | 138/179 | 0.75 (0.59, 0.95) | NA | Very Low |
Non-pharmacologic induction | |||||||
 Foley catheter vs. spontaneous labor | Retrospective cohort (1) |  | 221/375 | 3111/4263 | 0.81 (0.74, 0.88) | NA | Very Low |
 Membrane sweep vs. no membrane sweep/spontaneous labor | RCT (1) |  | 13/75 | 14/75 | 0.93 (0.47, 1.84) | NA | Very Low |
| Â | Retrospective cohort (1) | Â | 31/62 | 49/79 | 0.81 (0.60, 1.09) | NA | Very Low |
| Â | Â | Assisted | 13/62 | 19/79 | 0.87 (0.47, 1.62) | NA | Very Low |
| Â | Â | Unassisted | 18/62 | 30/79 | 0.76 (0.47, 1.24) | NA | Very Low |
 Amniotomy vs. spontaneous labor | Prospective cohort (1) |  | 39/62 | 65/96 | 0.93 (0.73, 1.18) | NA | Very Low |
| Â | Retrospective cohort (1) | Â | 477/575 | 3111/4263 | 1.14 (1.09, 1.18) | NA | Very Low |
 30 mL Foley catheter vs. 80 mL Foley catheter | RCT (1) |  | 18/77 | 15/77 | 1.20 (0.65, 2.20) | NA | Low |
| Â | Â | Assisted | 12/77 | 11/77 | 1.09 (0.51, 2.32) | NA | Low |
| Â | Â | Unassisted | 6/77 | 4/77 | 1.50 (0.44, 5.11) | NA | Low |
 Foley catheter vs. Amniotomy | Retrospective cohort (1) |  | 221/375 | 477/575 | 0.71 (0.65, 0.78) | NA | Very Low |
Pharmacologic vs. Non-pharmacologic or Combined (pharmacologic + non-pharmacologic) | |||||||
 Induction (Foley catheter, PGE2 or oxytocin) vs. spontaneous labor | Prospective cohort (1) |  | 33/52 | 193/268 | 0.88 (0.71, 1.10) | NA | Very Low |
 Induction (oxytocin, prostaglandin or amniotomy) vs. spontaneous labor | Prospective cohort (1) |  | 2165/3259 | 6477/8519 | 0.87 (0.85, 0.90) | NA | Very Low |
 Induction (oxytocin, prostaglandin, Foley catheter +/− surgical) vs. spontaneous labor | Retrospective cohort (1) |  | 1062/1576 | 3111/4263 | 0.92 (0.89, 0.96) | NA | Very Low |
 Oxytocin vs. Foley catheter | Retrospective cohort (1) |  | 183/254 | 221/375 | 1.22 (1.09, 1.37) | NA | Very Low |
 Oxytocin vs. Amniotomy | Retrospective cohort (1) |  | 183/254 | 477/575 | 0.87 (0.80, 0.95) | NA | Very Low |
 Oxytocin vs. Cook balloon + oxytocin | Retrospective cohort (1) |  | 106/150 | 32/64 | 1.41 (1.08, 1.84) | NA | Very Low |
 PGE2 vs. Foley catheter | Retrospective cohort (1) |  | 37/54 | 221/375 | 1.16 (0.95, 1.42) | NA | Very Low |
 PGE2 vs. Amniotomy | Retrospective cohort (1) |  | 37/54 | 477/575 | 0.83 (0.69, 0.99) | NA | Very Low |
 Double-balloon catheter + PGE2 vs. PGE2 | Prospective cohort (1) |  | 57/98 | 71/112 | 0.92 (0.74, 1.14) | NA | Very Low |
| Â | Â | Assisted | 10/98 | 13/112 | 0.88 (0.40, 1.92) | NA | Very Low |
| Â | Â | Unassisted | 47/98 | 58/112 | 0.93 (0.70, 1.22) | NA | Very Low |
 Oxytocin +/− amniotomy vs. amniotomy | Retrospective cohort (1) |  | 86/102 | 26/35 | 1.13 (0.92, 1.40) | NA | Very Low |
| Â | Â | Assisted | 17/102 | 4/35 | 1.46 (0.53, 4.04) | NA | Very Low |
| Â | Â | Unassisted | 69/102 | 22/35 | 1.08 (0.81, 1.44) | NA | Very Low |
  > 1 induction method vs. 1 induction method | Retrospective cohort (1) |  | 142/314 | 920/1259 | 0.62 (0.55, 0.70) | NA | Very Low |
 Induction (Oxytocin +/− Foley catheter +/− PGE1) vs. expectant management | Retrospective cohort (1) |  | 1088/1631 | 6787/11045 | 1.09 (1.05, 1.13) | NA | Very Low |
 Induction vs. no induction - Women with prior VD | Prospective cohort (3) Retrospective cohort (1) |  | 1383/1667 | 3802/4315 | 0.94 (0.92, 0.97) | 0 | Very Low |
 Induction vs. no induction - Women without prior VD | Prospective cohort (3) Retrospective cohort (1) |  | 1040/1980 | 3336/4970 | 0.75 (0.69, 0.81) | 35 | Very Low |