Abstract: This study investigated the characteristics of pelvic floor structure, pelvic floor function and muscle strength after cesarean section in re-pregnancy with scar uterus with a history of cesarean section. Selected 100 cases of pregnant women with scar uterus re-pregnancy and performed cesarean section as the observation group, and then selected 100 primiparas who received cesarean section during the same period as the control group. Transperineal pelvic floor ultrasound was used to evaluate and compare the pelvic organ movement parameters, levator ani muscle thickness, pelvic diaphragm hiatus parameters and muscle strength of the two groups from resting state to Valsalva state. The moving distance of bladder neck, external cervical orifice and rectum ampulla from resting state to Valsalva state in the observation group were all greater than those in the control group (P<0.05). In the resting state, Valsalva state, and retraction state, the thickness of the levator ani muscle of the observation group was smaller than that of the control group, and the transverse diameter of the pelvic hiatus, the anterior-posterior diameter of the pelvic fissure, and the area of the pelvic hiatus were larger than those of the control group (P<0.05). The surface electrical signals of pelvic floor muscle type I muscle fibers and type II muscle fibers in the observation group were lower than those in the control group, and the proportion of patients with abnormal vaginal pressure and pelvic floor muscle strength in the observation group was greater than that in the control group (P<0.05). Two weeks postpartum, the modified Oxford scale (MOS) pelvic floor muscle strength classification of the observation group was lower than that of the control group as a whole (P<0.05). The pelvic floor structure, pelvic floor function and muscle strength of the scarred uterus with a history of cesarean section are more serious than those of the first cesarean section, and postpartum rehabilitation should be strengthened for this group of people.

Key words: cesarean section, scarred uterus, pregnancy, pelvic floor structure, pelvic floor function, pelvic floor muscle strength