OBJECTIVE: To study the impact of controlled ovarian stimulation on ectopic pregnancy (EP) rate as a function of the number of oocytes retrieved, using donor IVF cycles as a control. DESIGN: Retrospective cohort study using a large national database. SETTING: Not applicable. PATIENT(S): Data from 109,140 cycles from the 2008-2010 SART registry, including 91,504 autologous cycles and 17,636 donor cycles in patients with non-tubal infertility. INTERVENTION(S): Varying amounts of oocytes retrieved in autologous and donor IVF. MAIN OUTCOME MEASURE(S): Ectopic pregnancy rates. RESULT(S): In autologous cycles, the EP rate significantly increased as oocyte yield increased. This association was not found in oocyte recipients. CONCLUSION(S): In autologous IVF cycles, increasing oocyte yield is correlated with a significantly increased EP rate. This association is not found in oocyte recipients, indicating that the increased EP rate may be due to the supraphysiologic hormone levels achieved with controlled ovarian hyperstimulation.