Impact of Body Mass Index on Surgical Outcomes in Gender-Affirming Vaginoplasty: A Retrospective Cohort Analysis.

OBJECTIVES: To diversify the understanding of Body Mass Index's (BMI) influence on vaginoplasty outcomes. As previous studies have assessed the role of increased BMI on gender-affirming vaginoplasty outcomes, no studies are currently published on the risks associated with an underweight BMI, nor do current studies present with statistical power due to limited sample sizes. This analysis represents the first and largest bidirectional assessment of BMI on vaginoplasty post-operative and functional outcomes. METHODS: A retrospective cohort study was conducted of 766 patients undergoing primary vaginoplasty between 2016 and 2023 at a single institution. The primary exposure was body mass index (BMI): underweight (<18.5 kg/m²), normal (18.5-24.9 kg/m²), overweight (25-29.9 kg/m²), and obese (≥30 kg/m²). Continuous variables were analyzed using Kruskal-Wallis tests, and categorical outcomes using Chi-square or Fisher's exact tests, with p<0.05 considered significant. The final dataset was analyzed using R version 4.5.1. RESULTS: Obese patients had significantly greater estimated blood loss (p<0.05). Postoperative urinary tract infection (UTI) rates differed by BMI (p=0.02), highest among underweight (14.8%) and obese (10.7%) groups. Surgical site infection (SSI) also varied by BMI (p=0.05), occurring primarily in underweight patients (3.7%). Partial graft failure requiring reoperation was more frequent among lower-BMI cohorts (p=0.04). All other complications did not differ significantly across groups. Functional outcomes were uniformly favorable, with tactile sensation (≥98%), cosmetic satisfaction (>97%), and penetrative intercourse ability (20-40%) consistent across BMI categories (p>0.05). CONCLUSIONS: Ultimately, BMI influences perioperative morbidity but should not preclude patients from gender-affirming vaginoplasty.