Impact of insulin resistance on <i>in vitro</i> fertilization outcomes in overweight and obese women: a retrospective cohort study

This retrospective cohort study evaluated 1,193 women undergoing first fresh IVF cycles to assess the effects of insulin resistance (IR) and overweight/obesity on outcomes. Participants were stratified by BMI and IR status. Overweight/obese women without IR exhibited comparable IVF outcomes to normal-weight controls. Untreated IR, however, significantly impaired outcomes, including fewer oocytes retrieved, 2PN zygotes, available embryos, and good-quality embryos all <i>p</i> ≤ 0.002), alongside lower fresh cycle live birth rates (34.4% vs. 53.3%, <i>p</i> = 0.038), implantation rates (32.1% vs. 47.8%, <i>p</i> = 0.023), cumulative pregnancy rates (45.8% vs. 68.4%, <i>p</i> = 0.001), and cumulative live birth rates (41.7% vs. 58.4%, <i>p</i> = 0.006). Notably, IR correction improved 2PN zygote formation (<i>p</i> = 0.026), numbers of available embryos (<i>p</i> = 0.021), fresh cycle live birth rates (57.6% vs. 34.4%, <i>p</i> = 0.034), cumulative pregnancy rates (63.2% vs. 45.8%, <i>p</i> = 0.018), and cumulative live birth rates (56.8% vs. 41.7%, <i>p</i> = 0.041). Multivariate analysis confirmed homeostasis model assessment of insulin resistance (HOMA-IR) as an independent negative predictor of live birth (OR = 0.49, 95% CI 0.30-0.82, <i>p</i> = 0.006). The findings challenge BMI-centric risk stratification in ART, emphasizing IR's role in compromising embryo quality and clinical outcomes. Preemptive IR screening and treatment in overweight/obese women are crucial.