Investigation of pelvic floor muscle properties during pregnancy and post-partum

Abstract

It is assumed changes occur to the biomechanics and viscoelastic responses of the pelvic floor muscles during pregnancy, however there is limited evidence of this. The primary goal of this thesis was to investigate the muscle properties of the pelvic floor muscles during pre-pregnancy, at two time points during pregnancy, and in the early post-partum period. As both instrumentation and clinical palpation measures were used at each stage of the study, a novel device was developed to quantify the subjective muscle stiffness measurements that are typically used in clinical practice. A further exploratory study was undertaken to confirm the positioning of the elastometer in vivo using magnetic resonance imaging. The findings from these studies demonstrated that temporal changes do occur during pregnancy, and in the first six months post-partum. Active force was significantly reduced from second trimester through to the post-partum period, while levator ani muscle stiffness was reduced only in those who had vaginal deliveries. This was supported by the ultrasound findings of increased levator hiatal area, and the associated increased symptoms of pelvic organ prolapse post-partum in women who gave birth vaginally. The elastometer was confirmed to be positioned correctly against the levator ani muscle, lending credence to the biomechanical measurements accurately. Quantification of clinical palpation for muscle stiffness showed poor consistency in the use of a seven-point palpation scale for subjective muscle stiffness, with a low probability of the clinician assigning the same stiffness values to the same scale category. In conclusion, the studies in this thesis contribute novel findings regarding the temporal changes to the biomechanical muscle properties of the pelvic floor, as well as challenging the current practice of physiotherapists’ use of digital palpation to assess muscle stiffness.