Received June 26, 2023
Accepted January 17, 2024

Objective: Evaluate the impact of possible maternal and paternal prognostic factors and ovarian stimulation protocols on clinical pregnancy and live birth rates in intrauterine insemination (IUI) cycles. Methods: Retrospective observational study of 341 IUI cycles performed from January 2016 to November 2020 at the Clinics Hospital of the Ribeirão Preto Medical School, University of São Paulo. Clinical pregnancy and live birth rates and their potential prognostic factors were evaluated. Wilcoxon’s non-parametric test was used to compare quantitative variables, and the chi-square test to compare qualitative variables, adopting a significance level of p<0.05. A logistic regression model was performed to verify which exploratory variables are predictive factors for pregnancy outcome. Results: The ovulation induction protocol using gonadotropins plus letrozole (p=0.0097; OR 4.3286, CI 1.3040 – 14.3684) and post-capacitation progressive sperm concentrations > 5 million/mL (p=0.0253) showed a statistically significant correlation with the live birth rate. Female and male age, etiology of infertility, obesity, multifollicular growth, endometrial thickness, and time between hCG administration and IUI performance were not associated with the primary outcomes. However, in the group of patients with ideal characteristics (women aged < 40 years, BMI < 30 kg/m², antral follicle count > 5, partner aged < 45 years, and post-capacitation semen with progressive spermatozoa > 5 million/mL), the rate of clinical pregnancy was 14.8%, while that of live birth, 9.9%. Conclusion: In this study, the ovulation induction protocol with gonadotropins plus letrozole and post-capacitation progressive sperm concentrations ≥ 5 million/mL were the only variables that significantly correlated with IUI success.