Age, obesity and vaginal deliveries (VD) are recognized risk factors for stress urinary incontinence (SUI). According to many authors, the abovementioned risk factors for incontinence also increase the risk of mid-urethral sling (MUS) failure. Our aim was to evaluate the objective and subjective effectiveness of retropubic MUS in 12 months observation, relative to the three potential risk factors of failure: obesity, age and VDs. A prospective observational study including 238 women who underwent retropubic MUS implantation was performed. Patients were divided into subgroups: obese vs non-obese, <65 vs ≥65 years old and no history of VD vs ≥1 VD. Follow-up took place between 6 and 12 months post-surgery. Cough test, 1-hour pad test, pelvic floor ultrasound examination, and Incontinence Impact Questionnaire 7 (IIQ-7) results were assessed pre- and post-operatively. Of the 238 patients, 208 (86.3%) completed a minimum follow-up period of 12 months. Significant improvement in the pad test was observed in all patients (83.2 ± 78.6 g vs 0.7 ± 3.3 g). Negative cough test results were obtained in over 94% of patients. Significant improvement in the IIQ7 results was observed in all patients (74.2 ± 17.7 vs 5.5 ± 13.4). No significant differences in all the analyzed parameters with regard to BMI, age and parity were observed. No combination of risk factors influenced the objective and subjective cure rates. Our study demonstrated that older age, obesity and history of VDs have no impact on objective and subjective sling effectiveness in a short term observation. There is no influence of combined demographic features on the failure risk.