In this study, 91 primiparous women were selected, with a period of post-delivery variable from 45 to 60 days. These patients were divided according to the type of delivery into three groups: I--consisting of 32 patients who had vaginal delivery; II--comprised 29 patients who were subjected to forceps; III--formed by 30 women who were subjected to cesarean section. Patients with a previous pregnancy were not included, so that the possible previous alterations of the pelvic floor did not interfere with the present evaluation. Patients with a pre-term pregnancy, fetus below 2,500 g or above 4,000 g, anomalous presentations, twin pregnancy, diabetes mellitus, systhemic arterial hypertension, hypertensive disease specific of pregnancy, endocrinopathies and neuropathies were also excluded. After 45 to 60 days from delivery the patients were subjected to anamnesis, gynecological examination, functional evaluation of the pelvic floor (FEAF), Q-Tip test and ultrasound of the bladder neck. As for the functional evaluation of the pelvic floor, it was observed that the patients with cesarean section presented better indexes compared to those who were subjected to forceps. The Q-Tip test showed that in both the patients from group I and group II bladder neck mobility was greater than in those from group III. Concerning bladder neck topography in relation to public symphysis and its mobility, which were evaluated by ultrasound, it was observed that at rest all the groups had the neck in a supra-pubic position, with no differences among them. Yet, during the required strain, the bladder neck stayed in the infra-pubic position with major frequency in group I. Bladder neck mobility was greater in the vaginal delivery group in relation to the other groups. It was also noticed that the group undergoing cesarean section showed less mobility. The obtained results lead us to conclude that despite the fact that vaginal delivery may cause displacement of the urethro-vesical junction during strain, and consequently greater bladder neck mobility, it is the attending physician's role to minimize the damage to the pelvic floor, thus avoiding the emergence of a predisposing factor to future stress urinary incontinence.