Ultrasonic Study On The Changes Of Structure And Muscle Strength Of Female Perineal Body Before And After Second Natural Delivery

Objective:To investigate the changes of structure and muscle strength of perineal body(PB)before and after the second natural delivery,and to provide clinical evidence for the early prevention and treatment of pelvic floor dysfunction.Methods:A total of 96 cases pregnant women with natural delivery in Nanchong Central Hospital were divided into primipara group(55 cases)and secondary multipara group(41 cases)according to the number of natural delivery.Each subject underwent a transperineal PB ultrasound imaging at three different time points:36-38 weeks of gestation,6-8 weeks and 3 months after delivery.The size(length,height,perimeter and area)of PB was observed and measured via a high-frequency linear array probe.The range of motion of PB was evaluated by measuring the difference of vertical distance between the ampulla of rectum and the horizontal line of the posteroinferior border of pubic symphysis under resting and maximum Vasalva state.Shear wave elastography was used to detect the Young’s modulus of PB,and the length,height,perimeter,area,range of motion and Young’s modulus of PB before and after delivery were compared between the two groups,and then the correlation between the above indicators was analyzed.Result:1.There were no statistically differences in age,pre-pregnancy body mass index,uterine height,abdominal circumference,prenatal body mass index,and neonatal birth weight between the two groups(P>0.05).2.The spontaneous tear rate of intact perineum in the secondary multiparous group was lower than that in the primiparous group,and the episiotomy rate was lower than that in the primiparous group.The difference was statistically significant(P<0.05).3.Changes of PB parameters before and after delivery in the two groups:primipara group:the size(length,height,perimeter,area)and Young’s modulus value of PB at 6-8 weeks after delivery and 3 months after delivery were significantly reduced compared with those at 36-38 weeks after delivery,and the range of motion was significantly increased(P<0.05);the size(length,height,perimeter,area)and range of motion of PB at 3 months after delivery were significantly reduced compared with those at 6-8 weeks after delivery(P<0.05),and the Young’s modulus value was significantly increased(P<0.05).Secondary multiparous women group:the size(length,height,circumference,area)and Young’s modulus value of PB at 6-8 weeks after delivery and 3 months after delivery were significantly reduced compared with those at 36-38 weeks of gestation,and the range of motion was significantly increased(P<0.05);the Young’s modulus value of PB at 3 months after delivery was significantly increased compared with that at 6-8 weeks after delivery(P<0.05),and there was no significant difference in size(length,height,circumference,area)and range of motion(P>0.05).4.Comparison between the two groups:the size(length,height,perimeter,area)of PB and Young’s modulus of PB in the secondary multiparous group were less than those in the primiparous group at the same time,and the difference was statistically significant(P<0.05);the PB activity in the secondary multiparous group was significantly increased compared with that in the primiparous group at 6-8 weeks after delivery and 3 months after delivery,and the difference was statistically significant(P<0.05),and there was no significant difference in PB activity between the two groups at 36-38 weeks of gestation(P>0.05).5.There was a significant negative correlation between the Young’s modulus value of PB and the range of motion(r=-0.493,P<0.001),and there was no significant correlation between the size(length,height,perimeter,area)of PB and the Young’s modulus value and the range of motion.Conclusion:1.PB damage caused by secondary natural delivery can gradually recover from self-recovery and cannot recover to pre-delivery levels from 3 months after delivery.2.The damage of PB in second natural delivery is larger than that in first delivery,and the recovery of PB after second natural delivery is slower than that after first postpartum.3.The change of Young’s modulus of PB after second natural delivery is earlier than the change of its shape and movement.Young’s modulus can be used as a monitoring index for early injury and recovery of PB,which has certain value in guiding postpartum pelvic floor rehabilitation.