Establishment and validation of a clinical prediction model for predicting early postpartum pelvic floor muscle weakness among primiparous women after vaginal delivery: a retrospective study.

Background: Pelvic floor muscle weakness (PFMW) is a significant postpartum complication linked to pelvic floor dysfunction. PFMW impairs quality of life and requires early intervention. This study aimed to develop and validate a clinical prediction model for early postpartum PFMW in primiparous women after vaginal delivery. Methods: This retrospective cohort study was conducted at a tertiary maternity hospital in Shanghai, China. Primiparous women with vaginal deliveries (July 2021-December 2023) were enrolled. Participants were assessed for PFMW using pelvic floor surface electromyography (sEMG) via the Glazer protocol at 42-90 days postpartum. Maternal and obstetric predictors were analyzed via univariable and multivariable logistic regression to construct a nomogram. Model performance was evaluated using concordance statistics (C-statistics), calibration curves, and decision curve analysis in both the training (n = 2,465) and validation (n = 1,049) cohorts. Internal validation was performed via ten-fold cross-validation. Results: Among 3,514 enrolled women, PFMW occurred in 25.55% (898/3,514), with comparable baseline characteristics between cohorts (age, pre-pregnancy BMI; P > 0.05). Multivariable analysis revealed five independent predictors: maternal age (OR 1.156, 95% CI 1.116-1.999), gestational weight gain (OR 1.146, 95% CI 1.116-1.178), instrumental delivery (forceps: OR 1.904, 95% CI 1.336-2.714), prolonged second stage of labor (OR 1.026, 95% CI 1.022-1.029), and infant weight (OR 1.003, 95% CI 1.002-1.003). The nomogram demonstrated strong discrimination [C-statistic: 0.866 (95% CI 0.850-0.882) in the training cohort; 0.870 (0.819-0.903) in the validation cohort] and good calibration. Decision curve analysis confirmed the clinical utility across threshold probabilities (0-0.3). Conclusion: This study established a validated nomogram integrating maternal and obstetric factors to predict early postpartum PFMW in primiparous women after vaginal delivery. This tool may aid in the early identification of high-risk individuals, enabling targeted rehabilitation to mitigate long-term pelvic floor dysfunction.