LAUSR

Do in-vitro-matured metaphase I (MI) oocytes have similar developmental potential as in-vivo-matured oocytes in preimplantation genetic testing (PGT) cycles? Blastocysts derived from in-vitro-matured MI oocytes demonstrate similar usable blastocyst rates compared to those derived from in-vivo-matured oocytes, offering clinical value in ART cycles. Approximately 15–20% of oocytes retrieved during ovarian stimulation are immature, often discarded due to their presumed low developmental potential. Rescue in-vitro maturation (IVM) has emerged as a potential method to utilize these immature oocytes, though their clinical utility remains controversial. Prior studies report mixed results regarding the developmental competence of embryos derived from in-vitro-matured MI oocytes. This retrospective study included 154 PGT cycles performed between January 2019 and December 2022. A total of 1,810 metaphase II (MII) oocytes were injected, comprising 1,577 in-vivo-matured and 233 in-vitro-matured MI oocytes. PGT cycles included preimplantation genetic testing for aneuploidy (PGT-A), structural rearrangements (PGT-SR), and monogenic disorders (PGT-M). Oocytes retrieved at the MI stage were cultured in vitro for up to 6 hours. Usable blastocysts were defined as euploid embryos suitable for transfer. Embryological and clinical outcomes were compared using statistical models controlling for confounding factors. The usable blastocyst rate was similar between in-vitro-matured MI oocytes and in-vivo-matured oocytes (adjusted RR 0.97, 95% CI 0.40–2.34). However, in-vitro-matured MI oocytes showed lower fertilization (50% vs. 74%, p < 0.001), cleavage (88% vs. 97%, p < 0.001), and blastocyst formation rates (41% vs. 66%, p < 0.001). Importantly, three live births were achieved using embryos derived from in-vitro-matured MI oocytes in patients with no usable in-vivo-matured oocytes. This study was retrospective and single-center, with a relatively small cohort of in-vitro-matured oocytes. Further prospective studies are needed to confirm the long-term safety and efficacy of rescue IVM. Rescue IVM offers a valuable opportunity to utilize immature oocytes, potentially increasing the number of viable embryos for patients with diminished ovarian reserve or poor ovarian response. This approach could reduce cycle cancellations and improve clinical outcomes in ART. Yes