Cesarean delivery is associated with elevated resting pelvic floor surface electromyographic activity in the early postpartum period: a retrospective cross-sectional study of 1,796 women

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Postpartum pelvic floor research has focused almost exclusively on weakness. Elevated resting pelvic floor activity, objectively measurable as increased resting surface electromyographic (sEMG) amplitude, is linked to pelvic pain and dyspareunia, yet its obstetric correlates remain unstudied. To identify factors associated with elevated resting pelvic floor sEMG activity in the early postpartum period, and to compare its risk profile with that of low fast-twitch sEMG amplitude. In this retrospective cross-sectional study of 1,796 women (median 49 days postpartum), elevated resting sEMG activity was defined as a pre-rest or post-rest baseline amplitude > 10 µV. We built sequential logistic regression models (demographic → obstetric → symptomatic) and performed subgroup, interaction, and sensitivity analyses, complemented by a threshold-free analysis of the continuous resting amplitude. A parallel model used low fast-twitch amplitude (< 20 µV) for contrast. Elevated resting sEMG activity was present in 194 of 1,776 evaluable women (10.9%). Cesarean delivery was the factor most strongly associated (adjusted OR 7.88, 95% CI 5.61–11.06), followed by younger age (OR 0.91 per year) and dyspareunia (OR 2.63, 95% CI 1.40–4.96). The association was robust across all sensitivity analyses (OR range 7.06–8.90), was confirmed in a threshold-free continuous analysis (adjusted geometric mean ratio 1.77, 95% CI 1.64–1.91), and showed no interaction by age or parity. The two sEMG-defined groups displayed partially contrasting risk profiles: cesarean delivery was inversely associated with low fast-twitch amplitude (OR 0.25), age effects ran in opposite directions, and only 0.6% of women exhibited both patterns. Elevated resting pelvic floor sEMG activity was common in this clinical cohort, strongly associated with cesarean delivery, and, in exploratory analyses, linked to dyspareunia. Whether assessing both contractile function and resting activity can guide group-specific rehabilitation warrants prospective study.