Immature oocyte proportion in a cohort led to poor embryo development but did not reduce clinical pregnancy rate

Purpose: This study aimed to evaluate the effects of immature oocyte proportion in a cohort on both IVF laboratory and clinical outcomes. Materials and methods: This retrospective cohort study took place at Morula IVF Jakarta Clinic from January 2016 to July 2020. A total of 1.826 couples undergoing IVF-ICSI/IMSI were included and classified into four groups according to the proportion of immature oocytes retrieved during OPU as follows: (1) immature ≤ 15% (n = 1.064), (2) immature 16–25% (n = 369), (3) immature 26–50% (n = 331), and (4) immature > 50% (n = 62). Primary outcomes were clinical pregnancy and miscarriage. Embryology laboratory results were assessed as the secondary outcomes. Statistical analyses were carried out utilizing Kruskal–Wallis or chi-square tests. p-value < 0.05 was considered statistically significant. Results: Increased proportion of immature oocytes in a cohort was significantly associated with body mass index, tubal factors, and estradiol level on trigger day (p < 0.05). Neither clinical pregnancy nor miscarriage was associated with the immature oocyte proportion (adjusted p-value = 0.872 and p = 0.345, respectively). However, a higher proportion of immature oocytes significantly reduced the total number of fertilized oocytes, number of top-quality cleavages, and blastocysts (p < 0.001). Furthermore, embryo transfer cancelation rates due to poor embryo quality were elevated significantly. Conclusion: Despite overall poor embryo development in the laboratory, our study seems to suggest that the proportion of immature oocytes in a cohort has no impact on clinical pregnancy and miscarriage rate in IVF program.