RESUMEN
Background: Herbal medicine could be effective at treating various illnesses. Hysteroscopy can be an effective method for assessing the uterus in terms of anatomical, physiological and pathological anomalies. Objective: This study aims to evaluate the effect of evening primrose oil (EPO) on cervical preparation in women candidates for hysteroscopy. Materials and Methods: This study was a double-blind, randomized controlled clinical trial including 160 women candidates for diagnostic hysteroscopy who were referred to Alzahra hospital from August 2019-March 2020. They were divided into 2 groups. Group A received 100 mg EPO as a soft gel capsule 6 hr before the hysterectomy in the posterior vaginal fornix. Group B received a placebo. After receiving the treatment, primary and secondary outcomes were evaluated in the groups. Results: The average Hegar size in the EPO group was larger than in the control group (p < 0.001 for both). Also, the need for mechanical dilation, the time taken until the first resistance and the time of dilatation completion in the EPO group were significantly less than in the placebo group (p < 0.008 for all). There was also greater ease of dilatation in the EPO group. Side effects such as uterine rupture, false passage, cervical rupture, allergic reaction, abdominal pain, nausea, diarrhea, headache and increase of bowel movements were not reported in any cases. Conclusion: Based on the findings of the present study, EPO is effective for cervical preparation in women undergoing hysteroscopy.