Correlation between immature oocytes counts and rates of oocyte maturity, fertilization and embryo development in ICSI cycles
Introduction: Several studies reported the effect of the number of oocytes retrieved on ART outcome. However, studies about the effect(s) of the number of immature oocytes retrieved on ART outcome are scarce. The goal was to evaluate the role of the number of immature oocytes on the rates of oocyte maturity, fertilization, and embryo development in ICSI cycles. Materials and Methods: Eighty ICSI cycles were included in this prospective evaluation. Patients were grouped according to the number of immature oocytes retrieved at follicular aspiration. Group A consisted of women with ≤ 2 immature oocytes and group B with > 2 immature oocytes. In the sub-analysis, correlation between numbers of GV and M1 oocytes with rates of fertilization and embryo development were assessed. In addition, the correlation between the numbers of immature and mature oocytes, as well as maternal age between two groups, was analyzed. To verify fertilization, 16-18 hr post ICSI, the oocytes were checked for the presence of pronuclei. Assessments of embryo quality, development, and embryo transfer were done on day 2. Results: There was no correlation between the number of immature oocytes and the rates of mature ones in each cycle. There were no significant differences for the rates of fertilization and cleavage between two groups. However, the rate of high quality embryos was higher in group A (p=0.046). In sub-analysis for effect of the number of GV oocytes per cycle, no significant differences were noticed between two groups of ≤ 2 and > 2 GV oocytes for rates of fertilization and embryo development. Also, the number of M1 oocytes, fertilization rate and embryo quality were similar between two groups, but the rate of early cleaved embryos were higher in group with ≤ 2 M1 oocyte (p=0.015). There was difference for maternal age between two groups of A and B (p=0.049). Also, advanced maternal age was correlated with higher number of GV oocytes (p=0.017). Conclusion: Immature oocytes (especially at M1 stage) may have negative impacts on early development of embryos derived from cohort mature oocytes. Prospective, randomized studies with large sample size that take into account all the variables may elucidate the role of immature oocytes count on ICSI outcome.