Anatomical and functional changes in the lower urinary tract during pregnancy

Objective To assess the prevalence and the development of urinary incontine nce in nulliparous pregnant women, both subjectively and objectively, and t o investigate the relation of incontinence with the mobility of the urethro -vesical junction measured by perineal ultrasound. Design A prospective longitudinal study. Setting University Hospital and Martini Hospital Groningen, the Netherlands . Population A cohort of 117 nulliparous pregnant women and 27 nulliparous no n-pregnant controls. Methods Urinary incontinence was measured by a questionnaire and by a 24-ho ur pad test. The position of the urethro-vesical junction and its mobility were measured by perineal ultrasound. Main outcome measure Prevalence of urinary incontinence; mobility of the ur ethro-vesical junction, indicated by the displacement/pressure coefficient. Results Up to 35% of the women reported urinary incontinence in pregnancy, and 20% of the women had a positive pad test. The angle of the urethro-vesi cal junction angle at rest and the displacement/pressure coefficient during coughing showed a significant increasing trend during pregnancy, but no ch anges were seen during the Valsalva manoeuvre. No relationship was found be tween subjective and objective incontinence data and the position and mobil ity of the urethro-vesical junction. Conclusion The prevalence of incontinence in nulliparous women as found by the pad test was significantly higher in pregnancy (20%) than in the non-pr egnant control group (4%). Perineal ultrasound of the urethrovesical juncti on showed lowering of the pelvic floor occurring as early as 12-16 weeks of pregnancy. Serial measurements of the displacement/pressure coefficient su ggest that the dynamic characteristics of the connective tissues of the pel vic floor remain unaltered,whereas a significant decrease in pelvic floor m uscle contraction occurs. Since no relation was found between measurements of the urethro-vesical junction and incontinence, urinary incontinence in p regnancy is most likely explained by other factors.