Introduction and hypothesis We hypothesized that upward bladder traction by visceral peritoneal closure during cesarean sections may have an impact on postpartum urinary complaints. Methods Based on a 90% power of the study and a 95% confidence interval, a sample size of 114 patients in each arm was needed to detect a 15% difference between both groups regarding postpartum urinary incontinence. To account for follow-up losses, we prospectively randomized 620 term primigravidas undergoing non-emergency cesareans into two groups (310 each): group 1, visceral peritoneal closure; group 2, non-closure. We compared perineal ultrasound findings 30 min before and 48 h after surgery. The UDI-6 questionnaire was used to assess urinary complaints. Results Group 1 showed significant widening of the posterior urethrovesical angle and alpha angle, more urethral descent 48 h postpartum and higher incidence of frequency, urge and stress incontinence 8 weeks postpartum. Symptoms disappeared almost completely after 6 months. Conclusions Compared to visceral peritoneal non-closure, cesarean with visceral closure is associated with significant postpartum frequency of urination and/or incontinence that disappear without treatment almost completely within 6 months.