Background/Aim: Not only the process of childbirth itself, but also processes during pregnancy seem to be strongly associated with urinary incontinence (UI). According to some epidemiological studies, UI during pregnancy occurs in 23–70% of the pregnant women. These studies also documented some risk factors (e.g., race, age, or body mass index). The aim of our study was to explore the prevalence of UI during pregnancy in the Czech Republic. Methods: 474 primiparas who gave birth at our maternity ward from June 14, 2004, through January 31, 2005, received a questionnaire. The questionnaire concentrated on the occurrence and presentation of UI before and during pregnancy . Results: 339 women (72%) completed the questionnaire. UI and the length of pregnancy are significantly related. We found a baseline UI prevalence before pregnancy of 17%, but before delivery one of 64%. We did not find any statistically significant relation between the prevalence of UI during pregnancy and body mass index before pregnancy as well as before delivery, weight gain during pregnancy, age, and birth weight. Conclusion: Our results show that pregnancy is a risk factor for the development of UI.