The effect of evening primrose oil on labor induction and cervical ripening: A systematic review and meta-analysis.

The evening primrose oil has prostaglandin effects and is applied to soften the cervix. This systematic review and meta-analysis aimed to establish the results of clinical trials performed on the effect of evening primrose oil on labor induction and cervical ripening in pregnant women. Research studies were searched from 1990 to September 2019 in Pubmed, Science Direct, Embase, and Cochrane Library using the keywords: cervical ripening, Bishop score, labor induction, post-term pregnancy, evening primrose, and any possible combination of these keywords (Farsi, English). Data analysis was conducted using STATA (version 14.1), and I2 index and random effect forest plots to assess the heterogeneity between the studies and perform the meta-analysis, respectively. Six articles that met the inclusion criteria were extracted in which four were entered into quantitative meta-analysis. The results' high heterogeneity was 91.4% based on I2 index (p ≤ .001) and the random model was applied for meta-analysis. The result demonstrated no significant difference between the intervention and control groups in terms of mean difference of the Bishop score before and after intervention (SMD: 0.27, 95%CI: -0.41, 0.96, p = .43). Based on current meta-analysis on four studies, effectiveness of oral consumption of evening primrose on cervical ripening was not approved.