Background <p>Endometriosis and body mass index (BMI) are known to influence reproductive outcomes, but their combined impact on in vitro fertilization (IVF) success remains uncertain.</p> Objective <p>To evaluate the relationship between BMI and the risk of endometriosis, and to assess how endometriosis—with or without prior surgical treatment—affects IVF outcomes, including oocyte yield, maturity, clinical pregnancy rates, and live birth rates.</p> Methods <p>This meta-analysis included 19 studies identified through comprehensive searches of databases including PUBMED, MEDLINE, and EMBASE. Primary outcomes assessed were the association between BMI and endometriosis risk, number of oocytes retrieved, and number of mature oocytes (MII). Secondary outcomes included clinical pregnancy rates, live birth rates, and the influence of prior surgery on IVF outcomes in women with endometriosis.</p> Results <p>BMI significantly influenced the risk of endometriosis, with obese women showing an increased risk (OR: 2.28) and normal-weight women showing a protective effect (OR: 0.45). Women with endometriosis had fewer total oocytes (mean difference [MD]: −2.06) and mature oocytes (MD: −2.07) compared to women without endometriosis undergoing IVF. While clinical pregnancy rates were not significantly different between groups (OR: 1.03), live birth rates were significantly lower in the endometriosis group (OR: 0.87). In a subgroup analysis of women who underwent prior surgical treatment for endometriosis, no improvement was observed in clinical pregnancy rates (OR: 0.79), and live birth rates were further reduced (OR: 0.67).</p> Conclusions <p>Higher BMI is associated with an increased risk of endometriosis, which negatively affects IVF outcomes by reducing oocyte yield and live birth rates. Prior surgical treatment does not appear to enhance IVF success and may further compromise live birth outcomes.</p>