Time-Series Analysis of Pregnancy and Childbirth Effects on Pelvic Floor Muscle Electrophysiology and Morphology in...

This study examined the differential effects of pregnancy and parturition on electrophysiological and histomorphometric properties in rat pelvic floor muscle (PFM) groups to provide a theoretical basis for targeted electrical stimulation rehabilitation therapy for specific postpartum PFMs.

Nine-week-old female Sprague-Dawley rats were divided into control (virgin), pregnancy (15 and 20 days), and postpartum (1 day and 1, 2, and 4 weeks) groups (n = 5 per subgroup). PFM electromyography was recorded through multichannel needle electrodes, and differences in action potentials (APs) and latent periods were analyzed. Hematoxylin-eosin and Masson staining were used to observe muscle fiber morphology and quantify fiber area proportion.

Compared with controls, the levator ani AP amplitude was reduced in the 15- and 20-day pregnancy and 1-day postpartum groups (38.49(22.65-106.23), 180.94(49.39-321.41), and 392.07(308.73-443.47) μV vs. 603.91(552.25-708.13) μV; P = 0.014, 0.014, and 0.047, respectively), and latency was significantly prolonged at 1 day postpartum (2.138(2.128-2.175) vs. 2.115(2.089-2.135) ms, P = 0.016); both recovered to baseline by 1 week postpartum. No fluctuations were observed in anal or urethral sphincter parameters (P > 0.05). Compared with controls, the anal sphincter muscle fiber area percentage decreased in the 15- and 20-day pregnancy groups (44.08(26.44-47.74)% and 42.04(32.67-47.47)% vs. 57.60(50.04-65.45)%, P = 0.021 for both) but recovered to baseline at 1 day postpartum. The urethral sphincter muscle fiber area percentage remained stable (P > 0.05).

Pregnancy and parturition affect PFMs differently. The levator ani muscle undergoes reversible electrophysiologic changes, anal sphincter exhibits structural remodeling, and urethral sphincter maintains functional and structural stability.