Embryological and Clinical Outcomes of Oocytes Retrieved from the Pouch of Douglas During Transvaginal Oocyte Pick-Up

Background/Objectives: Oocytes retrieved from the pouch of Douglas during transvaginal oocyte pick-up (OPU) have historically been described mainly in isolated case reports and small series. Their developmental competence and clinical relevance remain incompletely characterized. This study aimed to evaluate the embryological and clinical outcomes of oocytes recovered from pouch of Douglas fluid and to compare developmental outcomes between ovarian-derived and pouch of Douglas-derived oocytes. Methods: This retrospective observational study was conducted at a tertiary referral university hospital IVF center. Clinical and embryological data collected between February 2023 and June 2025 were retrospectively analyzed. A total of 2423 OPU cycles were screened, and 49 cycles with ≥2 cm of free fluid in the pouch of Douglas before OPU met the inclusion criteria. Following completion of ovarian follicular aspiration, free peritoneal fluid from the pouch of Douglas was aspirated separately and assessed for the presence of oocytes. Cycles were categorized according to whether oocytes were identified in the pouch of Douglas. Baseline cycle characteristics, ovarian response parameters, embryological outcomes, and clinical outcomes were evaluated. Developmental outcomes of ovarian-derived and pouch of Douglas-derived oocytes were compared within the same cycles. Results: Oocytes were recovered from pouch of Douglas fluid in 30 of 49 cycles (61.2%). Baseline characteristics, trigger-day hormonal parameters, follicle numbers, and ovarian embryological outcomes were similar between cycles with and without pouch of Douglas oocytes. A total of 44 oocytes were retrieved from pouch of Douglas fluid, of which 36 (81.8%) were metaphase II (MII) oocytes. Twenty-six oocytes demonstrated normal fertilization (2PN), with subsequent cleavage-stage and blastocyst-stage embryo development observed. No significant differences were observed between ovarian-derived and pouch of Douglas-derived oocytes in fertilization or embryo development rates. The proportion of MII oocytes was significantly higher among pouch of Douglas-derived oocytes (81.8% vs. 66.2%, p = 0.021). Five embryo transfers involving embryos derived from pouch of Douglas oocytes resulted in clinical pregnancy and live birth, including three transfers exclusively involving pouch of Douglas-derived embryos. No procedure-related complications were observed. Conclusions: Oocytes recovered from pouch of Douglas fluid demonstrated fertilization capacity, embryo developmental potential, and the ability to contribute to clinical pregnancy and live birth. These findings suggest that free peritoneal fluid identified before OPU may contain developmentally competent oocytes that would otherwise remain unrecovered. Given the retrospective design, limited number of embryo transfers, and uncertainty regarding the precise origin of these oocytes, the findings should be considered exploratory and require confirmation in larger prospective studies.