A Cochrane review [Abstract] 1 included 61 studies with a total of 12 819 subjects. Oxytocin alone compared with expectant management (6 660 women) reduced the rate of unsuccessful vaginal delivery within 24 hours (8.4% vs 53.8%, RR 0.16, 95% CI 0.10 to 0.25; 3 studies, n=399) but the caesarean section rate was increased (10.4% vs 9.0%, RR 1.17, 95% CI 1.01 to 1.35; 24 studies, n=6620). The use of epidural analgesia was increased when oxytocin alone was compared with expectant management or no treatment (RR 1.10, 95% CI 1.04 to 1.17; 10 studies, n=5150). Fewer women were dissatisfied with oxytocin induction in the one trial reporting this outcome (5.9% versus 13.7%, RR 0.43, 95% CI 0.33 to 0.56).
Oxytocin alone compared with vaginal PGE2 (4 564 women) was associated with an increase in unsuccessful vaginal delivery within 24hours in the two trials reporting this outcome (70% vs 21%, RR 3.33, 95% CI 1.61 to 6.89; 2 studies, n=58), but there was no difference in caesarean section rates (oxytocin 12.1% vs PGE2 10.9%, RR 1.11, 95% CI 0.94 to 1.30; 26 studies, n=4514). There was a small increase in epidurals when oxytocin alone was used (RR 1.09, 95%CI 1.01 to 1.17; 6 studies, n= 2949). Most of the studies included women with rupturedmembranes, and there was some evidence that vaginal prostaglandin increased infectionin mothers (chorioamnionitis oxytocin vs. PGs, RR 0.66, 95% CI 0.47 to 0.92; 4 studies,n= 2742) and babies (use of antibiotics RR 0.68, 95% CI 0.53 to 0.87; 2 studies, n=2564).These data should be interpreted cautiously as infection was not pre-specifiedin the original review protocol. Oxytocin alone compared with intracervical PGE2 (1 331 women) was associated with an increase in unsuccessful vaginal delivery within 24hours (50.4% versus 34.6%, RR 1.47, 95% CI 1.10 to 1.96; 2 studies, n=258) and an increase in caesarean sections (19.1% versus 13.7%, RR 1.37, 95% CI 1.08 to 1.74; 14 studies, n=1331).
A network meta-analysis 4 assessed the relative effectiveness, safety and cost-effectiveness of labour induction methods. 611 trials were included. The interventions most likely to achieve vaginal delivery within 24 hours were intravenous oxytocin with amniotomy (posterior rank 2; 95% credible intervals (CI) 1 to 9) and higher-dose (≥ 50 µg) vaginal misoprostol (rank 3; 95% CI 1 to 6) (table T1). Compared with placebo, several treatments reduced the odds of caesarean section, but there were considerable uncertainty in treatment rankings. For uterine hyperstimulation, double-balloon catheter had the highest probability of being among the best 3 treatments, whereas vaginal misoprostol (≥ 50 µg) was most likely to increase the odds of excessive uterine activity.
| Active intervention vs placebo | Odds ratio | 95% CI |
|---|---|---|
| iv. oxytocin with amniotomy | 0.05 | 0.07 to 0.32 |
| Vaginal misoprostol ≥ 50 μg | 0.09 | 0.06 to 0.24 |
| Titrated (low-dose) oral misoprostol solution | 0.10 | 0.07 to 0.29 |
| Vaginal misoprostol < 50 μg | 0.11 | 0.09 to 0.32 |
| Buccal/sublingual misoprostol | 0.11 | 0.05 to 0.19 |
| Vaginal PGE2 pessary (normal release) | 0.11 | 0.04 to 0.16 |
| Oral misoprostol tablet ≥ 50 μg | 0.16 | 0.05 to 0.20 |
| Double-balloon or Cook's catheter | 0.18 | 0.01 to 0.16 |
| Foley catheter | 0.19 | 0.09 to 0.46 |
| i.v. oxytocin | 0.20 | 0.21 to 1.97 |
Another Cochrane review [Abstract] 2 included 9 studies with a total of 2 391 subjects. There were no significant differences in rates of vaginal delivery not achieved within 24 hours (RR 0.94, 95% CI 0.78 to 1.14; 2 trials, n=1339) or caesarean section (RR 0.96, 95% CI 0.81 to 1.14; 8 trials, n=2023). There was no difference in serious maternal morbidity or death (RR 1.24, 95% CI 0.55 to 2.82; 1 trial, n=523), and no difference in serious neonatal morbidity or perinatal death (RR 0.84, 95% CI 0.23 to 3.12; 1 trial, n=781). In one trial high-dose oxytocin was associated with significantly shorter labors (difference 2 hours) without a significant difference in cesarean birth rates.
In an unblinded RCT 3 2-hourly 20 mcg oral misoprostol solution was compared to the standard intravenous oxytocin in labour induction in mothers (n=83) with pre-labour rupture of membranes at term. The overall induction success rates in the misoprostol arm was 81% versus 83% in the oxytocin arm (P = 0.447). The mean induction to vaginal delivery interval in the misoprostol arm was 8.4 hours as compared to 9.45 hours in the oxytocin arm (P = 0.116). The Caesarean section rates were 19% in the misoprostol arm and 17% in the oxytocin arm (P = 0.447), which was not statistically significant.
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