ABSTRACT
Objective:To speculate the effect of birth spacing on the pelvic floor type Ⅰ and Ⅱ fiber muscle strength of postpartum women with parities of two in different delivery modes.Methods:Totally 2 361 parturients who were investigated in Xuzhou Central Hospital from June 2016 to December 2020 were included in the questionnaire, clinical examination and pelvic floor surface electromyography assessment. According to the interval years between two parities and the pelvic floor typeⅠ and Ⅱ fiber muscle strength under different modes of delivery, curve fitting function equation was performed using curve regression method. The accuracy of the equation was verified by the receiver operating characteristic curve and the maximum area under the curve, and calculating the relative error rate.Results:A total of 2 357 parturients were included in the study and were divided into 4 groups based on delivery modes, women with both normal vaginal delivery were assigned to group A (589 cases); women with a first vaginal delivery and a second cesarean section were assigned to group B (480 cases); women with both cesarean deliveries were assigned to group C (1 273 cases); women with a first cesarean section and a second vaginal delivery were assigned to group D (15 cases). All of the curve fitting results were quadratic curves, and the appropriate interval years were selected when the muscle strength of type Ⅰ muscle fibers was>35 μV and that of type Ⅱ muscle fibers was>40 μV: 6-8 years in the group A, 5-10 years in the group B, and 1-11 years in the group C. The peak values of the quadratic curve were as follows: 7-8 years in the group A, 7-8 years in the group B, and 6 years in the group C. The maximum area under the curve of the function equations were all>0.6 (all P<0.05), the average relative error rate was 4.909%. Conclusions:The pelvic floor function of postpartum women with parities of two increases firstly and then decreases over time, showing a quadratic curve shape. In order to protect the pelvic floor function, the appropriate interval of birth spacing is 6-8 years.