3 53 Study Objective: to evaluate the efficacy of vaginal dinoprostone in reducing pain 54 perception during diagnostic office hysteroscopy (OH) in postmenopausal women. 55 Design: A randomized, double-blind controlled trial 56 Setting: tertiary University hospital 57 Participants: postmenopausal patients scheduled for OH. 58 Interventions: Eligible participants were randomized in a 1:1 ratio to dinoprostone and 59 placebo groups. The severity of pain was assessed with a visual analog scale (VAS) 60 ranging from [0= no pain and 10= worst pain] during and 30 minutes after OH. 61 Measurements and Main Results: the difference in the intensity of pain using VAS score 62 during the procedure. One hundred women (50 in each arm) were included in the study. 63 The mean VAS score during OH was significantly lower in the dinoprostone group than in 64 the placebo group (3.9±0.8 vs. 5.6±0.7, p<0.001). The passage of the hysteroscope through 65 the cervical canal was easier in the dinoprostone group (62.4±9.5 vs. 42.8±10.8, p <0.001). 66 Both groups were comparable regarding the duration of the procedure (p= 0.91) and the 67 rate of adverse effects. 68 Conclusion: Vaginal dinoprostone is effective in pain relief during diagnostic OH in 69 postmenopausal women with few adverse effects. 70 Keywords: office hysteroscopy; dinoprostone; prostaglandins; pain relief 71 Registry name: Clinical Trials.gov 72 URL:https://clinicaltrials.gov/ct2/show/NCT03683914?cond=dinoprostone+hysteroscopy 73 &rank=1 74 Registration number: NCT03683914 75 Date of trial registration: 22 September 2018 76 77 INTRODUCTION