The Effects of Oral and Vaginal Administration of Evening Primrose Oil on Cervical Ripening and Birth Outcomes: A Systematic Review and Meta-Analysis Publisher



Niazi A ; Ghavami V ; Beiranvandi F ; Golshan R P ; Feizabadi M N ; Fooladi E ; Moradi M
Source: Evidence Based Care Journal Published:2026

Abstract

Background: Given the conflicting results of three previous systematic reviews, drawing definitive conclusions about the effect of primrose oil on cervical ripening remains challenging. Aim: This meta-analysis aimed to identify and evaluate studies that have examined the effects of oral and/or vaginal evening primrose oil on cervical ripening and birth outcomes. Method: A comprehensive search of English and Persian articles from May 1990-March 2023 was performed in the PubMed, Web of Science, Cochrane Library, Scopus, SID and Magiran databases to identify randomized, placebo, controlled trials (RCTs) of primrose oil. Results: In the review of 16 RCTs, the results revealed a significant difference in the duration of the second phase of labor in the oral EPO capsule (mean difference (MD) = -9.68, 95% confidence interval (CI): -17.23, -2.14, I2 = 0%). Three studies reported significantly higher Bishop scores for the vaginal capsule in the EPO group than in the placebo group (MD=1.81, 95% CI: 0.24; 3.38, I2=100%). Three studies reported significant improvements in 5-minute Apgar scores with the use of the EPO vaginal capsule (MD = 0.60; 95% CI: 0.49, 0.71). Cesarean section rates were significantly lower in the group given vaginal EPO (odds ratio (OR) = 0.62; 95% CI: 0.40-0.96; I2 = 0.1%). Implications for Practice: Oral EPO shortens the duration of the second phase of labor and reduces cesarean section rates but does not yield a noteworthy increase in the Bishop score. Vaginal EPO seems to affect cervical ripening, reduce cesarean section rates, and improve 5-minute Apgar scores. © 2026, The Author(s).