OBJECTIVE : Defining patient characteristics that alter vascular anatomy at the sacrum is critical for avoiding life-threatening bleeding at the time of sacrocolpopexy. We tested the hypothesis that in thinner/older women, the bifurcations of the aorta and inferior vena cava (IVC) are lower relative to S1 resulting in less space accessible for suture/mesh placement, placing this group at increased risk of major vascular injury. METHODS : In a retrospective cross-sectional study, CT scans were used to make 2D measurements and a 3D model of the aorta/IVC, intervertebral disc space, and bony anatomy using segmentation and modeling software. For analysis, Spearman's and Pearson's correlation, Student's t test and the Mann-Whitney U test were used along with multivariate analysis of variance. RESULTS : Of eligible women who had undergone abdominal/pelvic CT, 107 were included. The median locations of the aortic and IVC bifurcations utilizing 2D analysis were at the inferior L4 and middle L5 vertebral body, respectively. In 10.2% of patients, the IVC was located at the L5-S1 disc space or lower; however, 3D modeling of this space which allowed assessment of the area below the S1 "drop off" showed that the amount of accessible space for suture/mesh placement was not decreased. Utilizing 2D analysis there was no statistically significant independent correlation between age or adiposity and the aortic or IVC bifurcation. Patients who were both elderly and thinner had a lower aortic bifurcation (p = 0.005) and a trend towards a lower IVC bifurcation (p = 0.082). CONCLUSIONS : In 10.2% of women, the IVC bifurcation descended at or below the L5-S1 disc space, suggesting that this group of women is at increased risk of major vascular injury. Patients who were both thin and elderly had lower bifurcations, but there was no difference in accessible surface area for suture placement on 3D analysis. 3D modeling improved visualization of the anatomy beyond the S1 "drop off" and may provide a future tool for surgical planning once predictors of high-risk anatomy are defined.