Efficacy and safety of oral and sublingual versus vaginal misoprostol for induction of labour: a systematic review and meta-analysis

Abstract

Objective: Misoprostol is a synthetic PGE₁ analogue that is used for induction of labour. Current guidelines support the use of doses that do not exceed 25 mcg in order to limit maternal and neonatal adverse outcomes. The present meta-analysis investigates the efficacy and safety of oral compared to vaginally inserted misoprostol in terms of induction of labor and adverse peripartum outcomes.

Methods: We searched Medline, Scopus, the Cochrane Central Register of Controlled Trials CENTRAL, Google Scholar, and Clinicaltrials.gov databases from inception till April 2022. Randomized controlled trials that assessed the efficacy of oral misoprostol (per os or sublingual) compared to vaginally inserted misoprostol. Effect sizes were calculated in R. Sensitivity analysis was performed to evaluate the possibility of small study effects, p-hacking. Meta-regression and subgroup analysis according to the dose of misoprostol was also investigated. The methodological quality of the included studies was assessed by two independent reviewers using the risk of bias 2 tool. Quality of evidence for primary outcomes was evaluated under the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework, ranging from very low to high.

Results: Overall, 57 studies were included that involved 10,975 parturient. Their risk of bias ranged between low-moderate. There were no differences among the routes of intake in terms of successful vaginal delivery within 24 h (RR 0.90, 95% CI 0.80) and cesarean section rates (RR 0.92, 95% CI 0.82, 1.04). Sublingual misoprostol was superior compared to vaginal misoprostol in reducing the interval from induction to delivery (MD - 1.11 h, 95% CI - 2.06, - 0.17). On the other hand, per os misoprostol was inferior compared to vaginal misoprostol in terms of this outcome (MD 3.45 h, 95% CI 1.85, 5.06). Maternal and neonatal morbidity was not affected by the route or dose of misoprostol.

Conclusion: The findings of our study suggest that oral misoprostol intake is equally safe to vaginal misoprostol in terms of inducing labor at term. Sublingual intake seems to outperform the per os and vaginal routes without increasing the accompanying morbidity. Increasing the dose of misoprostol does not seem to increase its efficacy.

Clinical trial registration: Open Science Framework ( https://doi.org/10.17605/OSF.IO/V9JHF ).

Keywords: Induction of labour; Maternal morbidity; Meta-analysis; Misoprostol; Neonatal morbidity; Oral; Sublingual; Systematic review.

Fig. 1

Summary risk of bias 2 (RoB 2) plot

Fig. 2

Forest plots of vaginal delivery within 24 h from onset of induction among parturient induced with oral misoprostol (subgrouped to sublingual and per os intake) and those induced with vaginally inserted misoprostol. (Vertical line = "no difference" point between the two groups. Blue squares = risk ratios; Diamonds = pooled risk ratios and 95 confidence intervals for all studies; Horizontal black lines = 95% CI; Horizontal red line = pooled 95% prediction intervals)

Fig. 3

Forest plots of risk of delivering with cesarean section among parturient induced with oral misoprostol (subgrouped to sublingual and per os intake) and those induced with vaginally inserted misoprostol. (Vertical line = "no difference" point between the two groups. Blue squares = risk ratios; Diamonds = pooled risk ratios and 95 confidence intervals for all studies; Horizontal black lines = 95% CI; Horizontal red line = pooled 95% prediction intervals)