Indices for studying urinary incontinence and levator ani function in primiparous women.

Urinary incontinence (UI) is a complex phenomenon that is prevalent in pregnant and parous women and requires the use of sophisticated measures to adequately reflect functioning of the continence system. The purpose of this study was to develop reliable and valid measures of UI and levator ani function for use in research and clinical settings. A Leakage Index (LI) and a Levator Ani Function Index (LAFI) were developed using data from a longitudinal study of primiparous women. Reliability and validity tests were conducted to: (i) estimate the internal consistency reliability of each index, (ii) determine whether the indices captured change in continence status and pelvic floor function during pregnancy through 1 year postpartum, and (iii) estimate association between the indices as a test of predictive validity. Cronbach's alpha ranged from 0.72 to 0.84 for the LI and from 0.53 to 0.79 for the LAFI across the six data collection time points of the study. Average LI scores increased late in pregnancy and decreased postpartum, though not significantly. Average LAFI scores decreased significantly at 35 weeks gestation (t = 4.84, P = 0.000) and increased significantly at 12 months postpartum (t = -3.51, P = 0.002) relative to baseline. The LI and LAFI were significantly associated at 20 weeks gestation (Pearson r = -0.40, P = 0.007) and at 6 weeks postpartum (Pearson r = -0.33, P = 0.029). The findings suggest the LI and LAFI are reliable and valid measures of UI and levator ani function in primiparous women, which can be used with confidence in clinical and research settings.