- Objective To evaluate the effects of ovarian endometrioma on the number of oocytes retrieved for IVF. Design Retrospective case control study. Setting University-based tertiary medical center. Patient(s) We studied 81 women with unilateral endometrioma who underwent their first IVF cycle. Intervention(s) Oocyte collection. Main Outcome Measure(s) The numbers of antral follicles and the retrieved oocytes in the ovary that contained endometrioma were compared with those from the contralateral ovary. Antral follicle count and the total number of oocytes retrieved from these women then were compared with those in 162 age-matched women with no endometrioma or endometriosis, who also underwent the first IVF treatment cycle. Result(s) There was no significant difference in the number of antral follicles and oocytes retrieved in the endometrioma-containing ovary (6.0 ± 0.4 and 7.7 ± 1.0, respectively) and in the opposite ovary (6.1 ± 0.5 and 8.5 ± 0.9, respectively). There was no correlation between the size and the number of endometriomas with the number of retrieved oocytes. Antral follicle count and the number of retrieved oocytes in these women (15.0 ± 1.6 and 11.9 ± 0.8) were similar to those in women with no endometrioma (14.2 ± 1.4 and 11.4 ± 0.5, respectively). Conclusion(s) The presence of ovarian endometrioma in a controlled ovarian hyperstimulation cycle for IVF treatment is not associated with a reduced number of oocytes retrieved from the affected ovary.