Objective: To determine the association between advanced pelvic organ prolapse and changes in lumbar lordosis and/or pelvic inlet orientation. Methods: Lateral lumbosacral spine/pelvic x-rays were taken of women with grade 2 or greater uterovaginal prolapse and women with grade 1 or less prolapse standing in their usual upright posture. The angles of lumbar lordosis and the pelvic inlet were measured by a radiologist who was masked to the pelvic examination findings. Results: Twenty women with prolapse were matched with 20 women without significant prolapse. There were no significant differences in the mean (± standard deviation [SD]) age (55.3 ± 9.0 years compared with 53.4 ± 9.5 years), body mass index (BMI) (28.9 ± 5.6 compared with 28.4 ± 5.2), gravidity (5.6 ± 3.5 compared with 5.0 ± 2.7), and vaginal parity (4.65 ± 3.3 compared with 4.5 ± 2.9) between the prolapse and nonprolapse groups, respectively. All participants were vaginally parous. The mean lumbar lordotic angle in women with pelvic organ prolapse (32.0° ± 9.8°) was significantly lower than that of controls (42.4° ± 10.9°) (P < .003). The mean angle of the pelvic inlet in women with pelvic organ prolapse (37.5° ± 7.0°) was significantly larger than that of controls (29.5° ± 7.3°) (P < .001). The differences in the mean angles of lumbar lordosis and the pelvic inlet, between the case and control groups, remained significant after multivariable logistic regression was performed. Conclusion: Women with advanced uterovaginal prolapse have less lumbar lordosis and a pelvic inlet that is oriented less vertically than women without prolapse.