Tehran University of Medical Sciences Journal of Family and Reproductive Health 1735-8949 8 1 2014 03 15 1 5 Nahid Sakhavar Obstetrics & Gynecologist Department, Zahedan University of Medical Science, Zahedan, Iran. Mania Kaveh Obstetrics & Gynecologist Department, Zahedan University of Medical Science, Zahedan, Iran. Kambiz Sadegi Anesthesiology Department, Zabol University of Medical Science, Zabol, Iran. 2015 10 16 Objective: To compare the effectiveness of letrozole and clomiphene citrate (CC) on uterine blood flow rate in patients with unexplained infertility. Materials and methods:In this randomized clinical trial 90 women with unexplained infertility referred to a university clinic from January 2011- December 2013 were enrolled. Thirty patients were randomized for letrozole, 30 patients for CC and 3o patients for control group. On the day 3 of cycle the patients were given letrozole 2.5mg/day or CC 100 mg /day orally or did not receive any treatment. Resistance index (RI) and pulsatility index (PI) of uterine artery were calculated and chemical pregnancy rate was evaluated. Results:Mean age was 26.4±3.2 (20-33) and mean BMI was 26.3± 3.2. After treatment using ultrasonography the Resistance index (RI) and Pulsatility index (PI) showed no significant difference among three groups (P > 0.05). Pregnancy rate in letrozole group (58%) was more in comparison to CC (53.6%) and control groups (46%) but the difference was not significant (P > 0.05). Conclusion: Our study showed that letrozole and clomiphene citrate have comparable impact on uterine blood flow and pregnancy rate in women with unexplained infertility. https://jfrh.tums.ac.ir/index.php/jfrh/article/view/246 https://jfrh.tums.ac.ir/index.php/jfrh/article/download/246/241