ABSTRACT Objective To identify morphological features of the soft tissue and bony pelvis that could serve as predictive risk factors for the development of pelvic organ prolapse (POP) in adult women. Methods This case–control study compared the shapes of the pelvic floor soft tissue and bony pelvis between three groups: parous women with POP (cases); parous women without symptoms of POP (controls); and nulliparous women. The primary dataset comprised 21 women around 50 years of age (mean ± SD, 50.3 ± 1.3 years), with seven participants in each group. Landmarks on the pelvis and urogenital hiatus were collected on magnetic resonance imaging scans. Pelvic shape was analyzed using geometric morphometry and principal component analysis. The findings were validated in a small secondary dataset of four parous women in their 30s, of whom two had POP and two were controls. Results Significant differences were observed between cases, controls and nulliparae in the primary dataset when soft tissue shape and pelvic shape were analyzed together on principal component analysis. When the shape of the bony pelvis was considered alone, a significant difference was observed between cases and controls, with the former group exhibiting a mediolaterally wider pelvis with relatively short anteroposterior and craniocaudal diameters. This difference was generalizable to younger women in the secondary dataset. Conclusion The shape of the pelvis in adult women affects their risk for postpartum POP. © 2025 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.