Exploring the Potential of Metaphase I Oocytes Unresponsive to Rescue IVM: Fertilization, Embryo Development, and Pregnancy Outcomes

Backround: The aim of thisprospectivecohortstudywastoevaluatethedevelopmentalpotential of metaphase I (MI) oocytes that failed to reach maturation following rescue in vitro maturation (IVM). Method: ICSI was performed to these oocytes and they were subsequentlyplaced in the calcium ionophore-containing medium for 20 minutes, washed in culture medium and incubated until fertilization assessment.In total of 263 patients and 276 ICSI cycles are included.Of these, 28 patients had onlyimmature oocytes that did not respond to IVM. Results: The mean age of the study population was 36.4±4 and the primary indication for treatment was low ovarian reserve, accounting for 39.3% of cases.The average number of retrieved oocytes was 6.7, the average count of MII oocytes was 4, while the average count of MI oocytes was 2. Fertilization of MI oocytes occurred in 17 out of 28 patients(60.7%).Among the fertilized zygotes, 29.4% were classified as Z2PN, while 52.9% were identified as Z3PN.Amoung 8 embryos that reached day 4; 5 were fresh trasnferred. One patient had ß HCG positivity. 3 embryos are frozen and thawed transferred; one patient had positive ß HCG. The clinical pregnancy rate was determined to be 25% (2/8). Only one pregnancy ended in live birth (live birth rate 12.5%). Conclusion: This study demonstrated the developmental potential of MI oocytes that failed to mature after rescue IVM. Utilizing these MI oocytes could increase the number of transferable embryos, enhance the efficiency of ICSI cycles, and improve pregnancy rates, as each embryo holds clinical significance.