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

PURPOSE: To evaluate the association between body mass index (BMI) and pregnancy outcomes in women receiving intrauterine insemination (IUI) treatment. METHODS: The study included 6407 women undergoing 13,745 IUI cycles stratified by BMI. Cox regression was used to analyze the association between BMI and cumulative live births across multiple IUI cycles. A generalized estimating equation (GEE) was used to analyze the live birth rate per cycle. RESULTS: Compared with normal-weight women (n = 4563), underweight women (n = 990) had a lower cumulative pregnancy and live birth rate (20.71% vs 25.93% and17.17% 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, the hazard ratio (HR) for achieving live birth following up to a maximum of four IUI cycles was 0.80 (95% CI: 0.67-0.95), comparing underweight with normal weight. In the GEE analyses, low BMI was also associated with a lower per-cycle birth rate (OR 0.79, 95% CI: 0.66-0.95), with adjustment for cycle-specific parameters, including ovarian stimulation, endometrial thickness, and follicular diameter. CONCLUSION: Low BMI is associated with poor IUI outcomes.