Functional disability mediates the relationship between pain severity and quality of life in pregnant women with pregnancy-related low back pain: a moderated mediation analysis.

BACKGROUND

Pregnancy-related low back pain (PLBP) significantly affects functional ability and quality of life (QoL), yet the underlying mechanisms remain unclear. This study examined the mediating role of functional disability between pain severity and QoL, as well as the moderating effects of gestational weeks and gestational body mass index (BMI).

METHODS

This cross-sectional study recruited 342 women with PLBP from medical centers and hospitals in southern Taiwan between February 2022 and January 2023. Pain severity was assessed using the Pain Visual Analog Scale (PVAS) and Brief Pain Inventory (BPI), functional disability using the Roland-Morris Disability Questionnaire (RMDQ) and Oswestry Disability Index (ODI), and QoL using the World Health Organization Quality of Life Assessment-Brief (WHOQOL-BREF). Moderated mediation analyses were performed using the PROCESS macro (Models 4 and 21) with 5,000 bootstrapped samples.

RESULTS

Functional disability (measured by RMDQ or ODI) significantly mediated the association between pain severity (PVAS or BPI) and QoL across four regression pathways. PVAS showed full mediation, with significant indirect effects through RMDQ (B = -0.701, 95% CI [-1.098, -0.384]), accounting for 61.1% of the total effect, and through ODI (B = -0.750, 95% CI [-1.156, -0.387]), accounting for 65.3% of the total effect. BPI exhibited strong partial mediation, with significant indirect effects through RMDQ (B = -0.074, 95% CI [-0.130, -0.021]), accounting for 45.1% of the total effect, and through ODI (B = -0.082, 95% CI [-0.134, -0.033]), accounting for 50.0% of the total effect, alongside marginally significant direct effects (p = 0.044-0.051). Gestational weeks moderated the relationship between pain severity and functional disability (B = 0.003-0.066, p = 0.001-0.029), with impairment worsening as pregnancy progressed. Gestational BMI moderated the effect of functional disability on QoL (B = -0.041 to -0.032, p = 0.011-0.035), exerting a stronger moderating effect than gestational weeks. Their interaction effect was minimal.

CONCLUSION

Functional disability is a key mechanism linking PLBP severity to reduced QoL. Gestational weeks and gestational BMI independently worsen these effects. Early functional assessment, functional rehabilitation, and weight management during pregnancy are essential strategies to minimize PLBP-related disability and promote maternal well-being.