en Reproductive Health Reproductive Health پژوهشي Original Research <div style="text-align: justify;"><span style="font-size:11pt"><span style="line-height:14.0pt"><span style="text-autospace:none"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">Background:</span></span></b><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times=""> Intrauterine insemination (IUI) is a commonly used first</span></span><span style="font-size:10.0pt"><span mincho="" ms="" style="font-family:">‑</span></span><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">line fertility treatment, yet pregnancy rates vary widely, and the relative influence of maternal and paternal factors remains unclear. Few studies have evaluated these determinants simultaneously, creating a gap in evidence for optimizing patient selection. This study examined key maternal and semen</span></span><span style="font-size:10.0pt"><span mincho="" ms="" style="font-family:">‑</span></span><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">related predictors of IUI success.</span></span></span></span></span></span><br /> <span style="font-size:11pt"><span style="line-height:14.0pt"><span style="text-autospace:none"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">Methods:</span></span></b><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times=""> This retrospective descriptive</span></span><span style="font-size:10.0pt"><span mincho="" ms="" style="font-family:">‑</span></span><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">analytical study included 211 infertile couples undergoing 335 IUI cycles at an academic infertility center between 2017 and 2018. Eligible couples had &ge;1 year of infertility, normal semen thresholds (motility &ge;20%, total count &ge;4 million, morphology &ge;4%), no severe systemic disease, and complete follow</span></span><span style="font-size:10.0pt"><span mincho="" ms="" style="font-family:">‑</span></span><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">up. Maternal variables included age, body mass index (BMI), endometrial thickness, follicle size, and number of mature follicles. Paternal variables included sperm count, progressive motility, and morphology. Pregnancy outcomes were assessed using &beta;</span></span><span style="font-size:10.0pt"><span mincho="" ms="" style="font-family:">‑</span></span><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">hCG testing and confirmed by ultrasound. Associations were examined using standard comparative analyses.</span></span></span></span></span></span><br /> <span style="font-size:11pt"><span style="line-height:14.0pt"><span style="text-autospace:none"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">Results:</span></span></b><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times=""> The pregnancy rate was 20.4% per couple and 12.8% per cycle. Endometrial thickness was significantly greater in successful cycles (8.3 &plusmn; 0.9 mm) compared with unsuccessful cycles (7.4 &plusmn; 1.7 mm; p = 0.002). Shorter infertility duration (p = 0.007) and fewer IUI attempts (p = 0.037) also predicted success. Maternal age, BMI, sperm count, progressive motility, and morphology showed no significant associations with pregnancy.</span></span></span></span></span></span><br /> <span style="font-size:11pt"><span style="line-height:14.0pt"><span style="text-autospace:none"><span calibri="" style="font-family:"><b><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">Conclusion:</span></span></b><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times=""> Endometrial thickness was the strongest predictor of IUI success, with optimal outcomes observed at 7&ndash;9 mm. Infertility duration and number of IUI attempts also influenced pregnancy likelihood, while semen parameters and most maternal characteristics did not. These findings highlight the importance of uterine receptivity and timely intervention. Further multicenter studies with additional biomarkers are recommended to enhance predictive models and guide individualized fertility care.</span></span></span></span></span></span></div> Endometrial thickness, Fertility factors, Infertility outcomes, Intrauterine insemination semen analysis 13 19 http://caspjrm.ir/browse.php?a_code=A-12-173-3&slc_lang=en&sid=1 Ramesh Baradaran Bagheri 10031947532846002728 10031947532846002728 No Atusa Karimi 10031947532846002729 10031947532846002729 Yes Reproductive Biotechnology Research Center, Avicenna Research Institute, ACECR, Tehran, Iran Zahra Sehat 10031947532846002730 10031947532846002730 No Mohammad Ali Rezaei mohammadrezaei362@gmail.com 10031947532846002731 10031947532846002731 No Alborz University of Medical Sciences, Karaj, Iran Naser Amrijanati 10031947532846002732 10031947532846002732 No