Objective: The purpose of this study was to investigate the influence of various factors on the outcome of intrauterine insemination (IUI) as a trial for improving the quality of health care provided for women with infertility problems as well as infertility center outcomes. Methods: Cohort study conducted over two years between December 2016 and December 2018 in IVF\ICSI center. Two hundred forty-nine couples diagnosed with different infertility etiologies underwent 487 cycles of IUI were enrolled. Ultrasound follicular measurements were recorded around time of ovulation as well as different factors were col- lected and compared between pregnant and non-pregnant groups. Main outcome measures were clinical pregnancy rate and risk of OHSS ac- cording to the woman's age, BMI, infertility type, different etiology of female infertility, the ovulation drug used and the quantity and size of ovarian follicles before hCG injection. Setting: Department of Obstetrics and Gynecology, Suez Canal Uni- versity Hospitals, Ismailia. Results:Pregnancy was achieved in 21.4% of cycles enrolled in the anal- ysis being significantly higher in women with mean follicular diameter of leading follicle of (19.8 +/- 1.97mm) in women with shorter infertility duration. The highest pregnancy rate was achieved in third IUI cycle. Conclusion: Leading follicle mean diameter of 19.8 mm was the op- timum diameter to trigger the ovulation and to have pregnancy. Early treatment of infertility is recommended as the success rate of IUI seems to get less with longer duration of infertility.