Pregnancy-related pelvic girdle pain and its relation to muscle function

Sammanfattning: Pregnancy-related lumbopelvic pain affects approximately 50% of all pregnant women. For the majority the pain disappears during the first  months after delivery; however, for a significant number of women, the pain is persistent, with little improvement for more than three months after delivery. Moreover, women who experience persistent lumbopelvic pain three months postpartum are at substantial risk for new episodes or for chronic lumbopelvic pain later in life. Hence, pregnancy-related lumbopelvic pain should be considered a major public health issue. In order to develop and offer specific treatment strategies, it is important to identify different subgroups of lumbopelvic pain based on different clinical presentations. Pelvic girdle pain (PGP) is one of the major subgroups of pain related to pregnancy. There is no consensus regarding the underlying mechanisms although instability in the pelvis has been proposed as one of the possible mechanism; thus, further studies are necessary to determine how to treat these women. The local lumbopelvic muscle system, including the pelvic floor muscles (PFM) is thought to contribute to the stabilization of the pelvis and they are also the target for many treatment strategies for lumbopelvic pain.The overall aim of this thesis was to improve rehabilitation for women with persistent postpartum PGP by investigating three areas, including: 1) the postural response of the PFM, 2) the effect of home-based specific stabilizing exercises (SSE) that target the local lumbopelvic muscle system and, 3) predictors for disability at 15 months postpartum.The thesis comprises three studies: A) a methodological study, B) an experimental study, and C) a clinical randomized controlled trial (RCT). The data is mainly based on muscle function, including recordings of electromyographic (EMG) activation, muscle endurance, and muscle strength. We also collected subjective ratings of disability, healthrelated quality of life, and pain.The methodological study showed that the designed protocol, which included limb movements performed at a comfortable speed in both standing and supine positions, was useful for detecting a postural response in the PFM. The experimental study demonstrated that women with persistent postpartum PGP and those free of pain exhibited a feed-forward mechanism in the PFM that responded in anticipation to leg lifts performed in a supine position. However, we cannot rule out the possibility that women with difficulties in transferring load between the trunk and legs (i.e., those with functional pelvic instability) might have a different postural response in the PFM. In the present study, one woman with persistent postpartum PGP failed to present a feed-forward mechanism in the PFM, in agreement with previous studies on other parameters of the PFM from other similar groups.The clinical RCT demonstrated that the concept of home-based SSE with visits every second week with the treating physiotherapist was not more effective than the clinical natural course for improving subjective ratings or muscle function in women with persistent postpartum PGP.A linear regression analysis revealed a complex picture that suggests that disability 15 months postpartum in women with persistent PGP could be partially predicted by two interaction effects comprising factors from different dimensions: biological, physical functioning, and self-rated function. The proposed association between muscle function and PGP was strengthen. New approaches are most likely needed to further identify subgroups of patients with persistent postpartum PGP that can be considered homogeneous for treatment.