Objective: To study the cumulative live birth rate (CLBR) after the first in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatment in women with or without deep-infiltrating endometriosis (DIE) and/or endometrioma diagnosed by transvaginal ultrasonography (TVUS), using the International Deep Endometriosis Analysis (IDEA) group definitions.<br /> Design: Prospective observational cohort study at a university hospital.<br /> Patients(s): In total, 1,040 women with subfertility aged 25 to %39 years were undergoing their first IVF/ICSI treatment between January 2019 and October 2022. Of these, 234 (22.5%; 95% confidence interval [CI], 20.0-25.0) women were diagnosed with DIE and/or endometrioma at systematic TVUS before starting their treatment.<br /> Intervention(s): All women underwent their first IVF or ICSI treatment. Fresh and/or frozen embryos from the first cycle were used until pregnancy was achieved or no embryos remained. Main Outcome Measure(s): Cumulative live birth rate after the first IVF/ICSI cycle in women with or without DIE and/or endometrioma. Result(s): The CLBR after the first IVF/ICSI treatment in the total cohort of women was 426/1,040 (41.0%; 95% CI, 38.0-44.0). Women with DIE and/or endometrioma had a lower CLBR (78/234, 33.3%; 95% CI, 27.3-39.4) than women without the disease (348/806, 43.2%; 95% CI, 39.8-46.6). The crude relative risk (RR) for cumulative live birth for women with DIE and/or endometrioma was 0.77; 95% CI, 0.63-0.94, and after adjustments were made for age, body mass index, s-antimu<euro>llerian hormone, stimulation protocol, and day for embryo transfer, the adjusted RR was 0.63; 95% CI, 0.48-0.82. There was no difference in the number of retrieved mature oocytes, fertilization rate, or good quality embryos between the 2 groups.<br /> Conclusion: The presence of DIE and/or endometrioma diagnosed by TVUS lowers the chance of live birth in women undergoing their first IVF/ICSI treatment. (Fertil Steril (R) 2024;121:832-41. (c) 2024 by American Society for Reproductive Medicine.)