Intravenous Oxytocin Alone for Cervical Ripening and Induction of Labour

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 (HASH(0x2fdd378) 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 (HASH(0x2fdd378) 50 µg) was most likely to increase the odds of excessive uterine activity.

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.

References

• Alfirevic Z, Kelly AJ, Dowswell T. Intravenous oxytocin alone for cervical ripening and induction of labour. Cochrane Database Syst Rev 2009;(4):CD003246. [PubMed]
• Budden A, Chen LJ, Henry A. High-dose versus low-dose oxytocin infusion regimens for induction of labour at term. Cochrane Database Syst Rev 2014;(10):CD009701.[PubMed]
• Mbaluka CM, Kamau K, Karanja JG et al. Effectiveness and safety of 2-hourly 20mcg oral misoprostol solution compared to standard intravenous oxytocin in labour induction due to pre-labour rupture of membranes at term: A randomised clinical trial at Kenyatta hospital. East Afr Med J 2014;91(9):303-10.[PubMed]
• Alfirevic Z, Keeney E, Dowswell T et al. Which method is best for the induction of labour? A systematic review, network meta-analysis and cost-effectiveness analysis. Health Technol Assess 2016;20(65):1-584.[PubMed]