Self-efficacy with Pelvic floor muscle training mediates the effect of an App-based intervention on improving postpartum urinary incontinence severity among pregnant women: A causal mediation analysis from a randomised controlled trial.

ABSTRACT

BACKGROUND: A pragmatic randomised controlled trial has confirmed the effectiveness of Urinary Incontinence for Women (UIW) app-based intervention in improving postpartum urinary incontinence (UI) severity among pregnant women. However, the causal mechanisms underlying this intervention effect remain unclear. OBJECTIVE: To examine the mediating role of self-efficacy with pelvic floor muscle training (PFMT) on the effect of the UIW app-based intervention in improving postpartum UI severity. METHODS: This was a secondary causal mediation analysis of a single-center, 2-arm, unblinded pragmatic randomised controlled trial. Singleton pregnant women without UI before pregnancy aged ≥18 years and between 24 and 28 weeks of gestation were recruited from a tertiary public hospital in China and randomised to receive the UIW app intervention plus oral PFMT instructions (n = 63) or oral PFMT instructions alone (n = 63). The primary outcome was postpartum changes in UI severity at 6 weeks. Changes in self-efficacy with PFMT 2 months after randomisation were a hypothesised mediator. Causal mediation analysis was used to estimate the average causal mediation effect (ACME), average direct effect (ADE), average total effect (ATE), and proportion mediated. A sensitivity analysis was conducted to examine the robustness of the ACME in relation to potential unmeasured confounding. RESULTS: Data from 103 participants were analyzed. The ATE of UIW app-based intervention on postpartum UI severity was 2.91 points (95 % confidence intervals [CI] 1.69 to 4.12), with ADE of 1.97 points (95 % CI 0.63 to 3.41) and the ACME 0.94 points (95 % CI 0.27 to 1.72). The proportion of ATE mediated by self-efficacy with PFMT was 0.32 (95 % CI 0.08 to 0.67). Sensitivity analysis revealed the robust ACME with respect to the potential effects of unmeasured confounding. CONCLUSION: An increase in self-efficacy with PFMT partially mediated the effect of the UIW app intervention on improvements in postpartum UI severity. TRIAL REGISTRATION The original trial was prospectively registered in the Chinese Clinical Trial Registry under the reference number ChiCTR1800016171 on 16/05/2018. Further details can be accessed at http//www.chictr.org.cn/showproj.aspx?proj=27455.