Low BMI is associated with poor IUI outcomes: a retrospective study in 13,745 cycles

Abstract Background: Although the effect of body mass index (BMI) on the outcome of in vitro fertilization (IVF) has been extensively studied, its correlation with intrauterine insemination (IUI) has rarely been reported. Therefore, we aimed to examine the impact of BMI on IUI outcomes．Methods: Six thousand four hundred and seven women undergoing 13,745 IUI cycles stratified by BMI were included in the study. Cox regression was used to analyze the association between BMI and cumulative live birth across multiple IUI cycles. Generalized estimating equation (GEE) was used to analyze the live birth rate per cycle.Results: Compared with normal weight women (n = 4,563), underweight women (n = 990) had a lower cumulative pregnancy and live birth rate (20.71% vs 25.93%, 17.17% vs 21.61%, respectively), while overweight women (n = 854) had a higher cumulative pregnancy and live birth rate (31.97%, 26.58%). Adjusted for confounders, hazard Ratio (HR) for achieving live birth following up to a maximal of 4 IUI cycles was 0.80 (95%CI: 0.67-0.95) comparing underweight with normal weight. In GEE analyses, low BMI was also associated with a lower per-cycle live birth rate 0.77 (95%CI: 0.64-0.92) with adjustment for cycle-specific parameters, including ovarian stimulation, endometrial thickness and follicular diameter.Conclusion: Underweight is associated with poor IUI outcomes.