Urinary incontinence is any involuntary passage of urine, which commonly prevalent health problems globally among pregnant women with varying between 6-75%. Aim of the study: determine prevalence and associated factors of urinary incontinence during third trimester of pregnancy. Subjects and design: A descriptive cross-sectional design was used on 233 pregnant women who chosen by systematic random sampling. Setting: at an Outpatient Antenatal Clinic of New Obstetric and Gynecological Hospital, Mansoura University, Egypt. Tool of data collection: Structured Interviewing Questionnaire which consists of four parts as demographic characteristics of pregnant women, obstetric and gynecological data, elimination habits , caffeine drinking and action taken when pregnant women have urinary incontinence. Results: current study showed that less than half the studied pregnant women had urinary incontinence, more than two third of them who had UI suffered in silence and ate high fiber diet and around half of them avoided laxatives, treat cough, maintain healthy weight, empty bladder completely and decrease performance of domestic activity. Regarding associated factors, present study showed that age25≥30, gravidity>3, parity2-3, C.S, baby weight at last delivery2.5-3kg, bronchial asthma, chronic cough, LSCS, constipation, caffeine drinking are associated factors of urinary incontinence Conclusion: Urinary incontinence was prevalent among studied pregnant women and previous C.S, baby weight, bronchial asthma, constipation are associated factors of urinary incontinence. Recommendations: All pregnant women should be screened for UI during antenatal visits , drinking plenty of fluid, eat high fiber diet, exercise regularly, proper toilet hobbits and healthy lifestyle choices