This study aimed to determine the efficacy of evening primrose oil versus dinoprostone gel as a cervical priming agent prior to operative hysteroscopy.

Nine patients were randomixed to receive either oral Evening Primrose Oil 1000mg/capsule one capsule three times a day for 7 days (n=4) versus 500 mcg intracervical dinoprostone gel 12 hours (n=5)prior to the procedure. The primary outcome measures were baseline cervical width prior to operative hysteroscopy. The secondary outcomes were surgeons' subjective assessments for insertion difficulty, number of patients requiring cervical dilatation, duration of cervical dilatation, pre-operative pain, adverse effects and complications.

Both agents, Evening primrose oil and dinoprostone gel, were effective for cervical dilatation with a mean cervical diameter of 8.0+1.4 mm and 8.2+1.3 mm, respectively (P=0.832). There are no significant difference in the mean cervical diameter, ease of insertion of operative hysteroscope, time required for and number of patients requiring cervical dilatation. More patients in the dinoprostone complained of hypogastric pain prior to the procedure. No perioperative complications were observed in both groups.

Both oral Evening primrose oil and intracervical dinoprostone gel were equally effective in inducing proper cervical priming prior to operative hysteroscopy. Nevertheless, Evening primrose oil may be superior due to its oral route, reduced cost, patient convenience and acceptability.