Figure 1. Study population enrollment flow chart. Among 635 cycles of ART performed at Toranomon Hospital from 2010 to 2019, 139 cycles were excluded because of previous ovarian surgery, previous chemotherapy, history of malignant tumor in male partner, oocyte cryopreservation, or blastocyst culture. The remaining 496 cycles represented our study population. Fifty-two cycles where women had a history of malignant tumor made up the case group. The 52 cycles in the control group were randomly chosen from the non-cancer study population by computer matching of propensity scores involving age and body mass index.