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

This study aimed to evaluate the effects of immature oocyte proportion in a cohort on both IVF laboratory and clinical outcomes. 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. 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. 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.