Cottrell, Cyra M.

Objective: Obesity is thought to negatively affect outcomes of in-vitro fertilization (IVF), however its impact on minimal stimulation (MiST) cycles is unclear. This study aims to explore the effect of elevated body mass index (BMI) on blastulation rate (BR) and clinical pregnancy rate (CPR) in patients undergoing MiST. Design: Retrospective cohort analysis of patients who underwent MiST at a single academic fertility center over four years. Patients were grouped by BMI to assess associations between BR and CPR. Materials and Methods: Patients aged 18-44 were identified who underwent MiST at Mayo Clinic between 10/1/2020, and 12/1/2024. BR was calculated as each patient’s total blastocysts divided by total 2PN embryos; embryos and blastocysts were pooled in those with multiple cycles. CPR was calculated as each patient’s total number of clinical pregnancies divided by total embryo transfers. Patients were stratified into two BMI groups: underweight/normal (BMI <25, n=58) and overweight/obese (BMI ≥25, n=76). Quasibinomial logistic regression evaluated the association between BMI (per 5-unit increase) and both BR and CPR. Results: 134 patients were identified. 58 patients in the normal BMI group underwent 117 stimulation cycles and 67 transfers. 76 patients in the elevated BMI group underwent 139 stimulation cycles and 81 transfers. Age and anti-mullerian hormone levels were similar between groups. In the normal BMI group, BR 59.6%, CPR 45.6%, and cumulative pregnancy rate 45.6%. In the elevated BMI group, BR 62.3%, CPR 45.8%, and cumulative pregnancy rate 58.8%. BR and CPR did not differ significantly between BMI groups (BR p=0.652; CPR p=0.982). Per logistic regression, increasing BMI was not significantly associated with BR (95% CI: 0.77-1.07, p = 0.25) or CPR (95% CI: 0.76-1.30, p = 0.94). Conclusions: In this cohort, high BMI was not associated with significantly lower BR or CPR in patients undergoing MiST. Support: Institutional research funding.