The role of maternal weight, body composition, systemic inflammation, and mental health in pregnancy-related lumbopelvic pain: a study protocol

Abstract

Abstract: Introduction Pregnancy-related lumbopelvic pain (PLPP) affects 50 to 90% of pregnant women, yet its underlying mechanisms remain poorly understood, limiting effective prevention and treatment strategies [1]. Maternal weight and gestational weight gain are recognized as risk factors, but prior studies did not differentiate between fat and fat-free mass [2]. In non-pregnant populations, higher fat mass is associated with low back pain, potentially through adiposity-related systemic inflammation. This systemic inflammation is linked to depression, a known predictor of PLPP, and anxiety [3]. However, the combined and longitudinal contribution of maternal weight, body composition, inflammation, and psychological factors to PLPP remains unexplored.

This study aims (1) to determine whether (changes in) maternal weight and body composition predict the onset and persistence of PLPP, and (2) to examine the mediating and moderating roles of depression, anxiety, and systemic inflammation.

Methods This longitudinal cohort is part of the PROFit study (G0A1N24FWO/S69463). A total of 211 pregnant women without PLPP in early pregnancy will be recruited and followed through the third trimester, as well as at six weeks and nine months postpartum. PLPP will be evaluated using patient-reported outcome measures of pain intensity and functioning, as well as clinical tests. Body composition will be measured using bioelectrical impedance analysis, and maternal weight and height will be recorded using a digital scale and stadiometer. Inflammatory markers will be measured using multiplex flow cytometry, and psychological factors will be assessed using validated questionnaires. Data will be analyzed using group comparisons, regression models, latent class growth analysis, and cross-lagged panel modelling.

Results (or hypothesis) We hypothesize that greater gestational weight gain, higher fat mass, and stronger inflammatory responses predict the onset and persistence of PLPP. Psychological factors, such as depressive and anxiety symptoms, are expected to mediate these relationships.

Process evaluation As of November 12, 2025, 27 participants (mean age=31.0, SD=3.6) have been included. Recruitment of participants remains the biggest hurdle of the study.

Conclusion This study will provide new insights into how maternal weight, body composition, inflammation, and mental health interact in the onset and persistence of PLPP, guiding the improvement of prevention and intervention strategies.