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Relative and Maximal Intra-abdominal Pressure and Postpartum Pelvic Floor Outcomes in Primiparas Delivered Vaginally

Supplemental digital content is available in the text. Objectives This study aimed to explore associations between relative and maximal intra-abdominal pressure (IAP) on pelvic floor outcomes in primiparas delivered vaginally. Methods At 5–10 weeks and 1 year postpartum, we measured absolute IAP by vaginal sensor while participants lifted a weighted car seat (IAPLIFT) and performed isometric trunk flexion endurance (IAPTFE) and seated maximal strain (IAPSTRAIN). Primary outcomes, completed 1 year postpartum, included worse pelvic floor support (descent to or beyond the hymen) and positive symptom burden (bothersome symptoms in ≥2 of 6 domains on the Epidemiology of Prolapse and Incontinence Questionnaire). We calculated relative IAP (as absolute IAP/IAPSTRAIN). Results Of 542 participants, 9.7% demonstrated worse support and 54.3% demonstrated symptom burden at 1 year postpartum. In multivariable analyses, absolute IAPLIFT and absolute IAPTFE at 5–10 weeks postpartum were not associated with worse support. As relative IAP at 5–10 weeks increased, the prevalence of worse support decreased (prevalence ratio [PR] of 0.77 [95% confidence intervals (CIs), 0.63–0.94] and PR of 0.79 [95% CI, 0.67–0.93]) per 10% increase for relative IAPLIFT and relative IAPTFE, respectively. This was largely due to IAPSTRAIN, which increased the prevalence of worse support (PR, 1.15 [95% CI, 1.06–1.25]) per 10 cm H2O increase. One year postpartum, only IAPSTRAIN increased the prevalence of worse support (PR, 1.11 [95% CI, 1.02–1.20]) per 10 cm H2O. Of all IAP measures at both time points, only absolute IAPLIFT at 1 year significantly increased the prevalence of symptom burden (PR, 1.11 [95% CI, 1.05–1.18]) per 10 cm H2O. Conclusions This exploratory analysis suggests that postpartum IAPSTRAIN may increase the prevalence of worse support in primiparas delivered vaginally.