Pregnancy outcomes decline with increasing body mass index: Analysis of 239,127 fresh autologous in vitro fertilization cycles from the 2008-2010 Society for Assisted Reproductive Technology registry

Objective To examine the effect of body mass index (BMI) on IVF outcomes in fresh autologous cycles. Design Retrospective cohort study. Setting Not applicable. Patient(s) A total of 239,127 fresh IVF cycles from the 2008-2010 Society for Assisted Reproductive Technology registry were stratified into cohorts based on World Health Organization BMI guidelines. Cycles reporting normal BMI (18.5-24.9 kg/m²) were used as the reference group (REF). Subanalyses were performed on cycles reporting purely polycystic ovary syndrome (PCOS)-related infertility and those with purely male-factor infertility (34,137 and 89,354 cycles, respectively). Intervention(s) None. Main Outcome Measure(s) Implantation rate, clinical pregnancy rate, pregnancy loss rate, and live birth rate. Result(s) Success rates and adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for all pregnancy outcomes were most favorable in cohorts with low and normal BMIs and progressively worsened as BMI increased. Obesity also had a negative impact on IVF outcomes in cycles performed for PCOS and male-factor infertility, although it did not always reach statistical significance. Conclusion(s) Success rates in fresh autologous cycles, including those done for specifically PCOS or male-factor infertility, are highest in those with low and normal BMIs. Furthermore, there is a progressive and statistically significant worsening of outcomes in groups with higher BMIs. More research is needed to determine the causes and extent of the influence of BMI on IVF success rates in other patient populations.