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.

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.