Results
Our study screened successfully in total 3385 subjects, including 1286 cases in CD group and 2099 cases in VD group. No significant differences were detected in age, BMI, gestational age at delivery, and neonatal weight between CD and VD (P > 0.05, table 1). Our analysis showed that the average peak amplitude of phasic (flick) contractions and the average mean amplitude of tonic contractions were both significantly higher in CD than in VD (P < 0.01, table 2). In contrast, CD had less the mean amplitude variability of tonic contractions than VD (P < 0.01, table 2). The results revealed that the muscle strength of fast muscle (class II fibers) and slow muscle (class I fibers) were higher in CD than in VD, and the variation of slow muscle (class I fibers) was significantly higher in the VD. For the comparison of the value at rest pre-baseline and post-baseline, CD had higher average mean amplitude compared to VD(P<0.01, table 2). It suggested that the PFM tension in a relaxed state were higher in CD than in VD. Our results showed that the engagement of the abdominal muscles in VD was significantly higher than that in CD(P<0.01, table 2).
We further differentiated as 4 subgroups of vaginal delivery. There was no statistically difference in maternal age, BMI, gestational age at delivery, and neonatal weight among the four subgroups of vaginal delivery (P > 0.05, Table 3). We identified the significant difference among the four subgroups of vaginal delivery group(Table 4). The average mean amplitude of rest pre-baseline was significantly higher in group B compared to group D (P=0.041, Fig.1). The average peak amplitude of phasic (flick) contractions (Fig.2) and the average mean amplitude of tonic contractions (Fig.3) in group D was statistically lower than the other vaginal delivery groups (P<0.05). The mean amplitude variability of tonic contractions was larger in group D than group A, B. (P was 0.002,0.003, respectively, Fig.4). The average mean amplitude of rest post-baseline was shorter in group D than groups A, B, and C (P was 0.000,0.000,0.003, respectively, Fig.5). There was no significantly difference in the engagement of the abdominal muscles among 4 subgroups of vaginal delivery(P > 0.05, Table 4).