Oocyte maturation-index as measure of oocyte cohort quality; a retrospective analysis of 3135 ICSI cycles

Objective: To investigate the use of an oocyte M-Index as a measure of the reproductive competence of oocyte cohorts collected following COS for ICSI. Design: A retrospective analysis of 3135 autologous ICSI cycles. Setting: A private IVF clinic. Materials and methods: Oocytes were denuded immediately after oocyte collection and the in vivo oocyte M-Index was calculated for the oocyte cohort collected (number of normal metaphase II oocytes per total number of normal oocytes collected). The measured outcomes were analyzed according to the M-Index (0–20%, 21–40%, 41–60%, 61–80%, and 81–100%) and female age (20–30, 31–40 years). Main outcomes: Clinical pregnancy. Results: 60,955 oocytes were collected from the 3135 ICSI cycles, 57,214 (93.9%) were normal and 39,364 (68.8%) of these were metaphase II oocytes. 71.6% of metaphase I oocytes reached nuclear maturity by the time of the ICSI procedure. Trend analyses of fertilization and clinical pregnancy to M-Index showed that fertilization increased significantly (p < 0.0001) with an increasing M-Index, from 64.0% (M-Index 0–20%) to 78.1% (M-Index 81–100%) as well as clinical pregnancy (p < 0.001) from 23.3% to 48.1%. No predictive threshold value could be determined from the data using ROC analysis. Analyzing the data across a 40% M-Index cut-point, both embryology and clinical pregnancy outcomes were significantly higher for cycles with an M-Index of >40%. Conclusion: Our analysis shows that a simple maturation index calculated at the time of oocyte collection in a given ICSI cycle provides important prognostic information with regard to potential pregnancy outcomes and may reflect the importance of cytoplasmic maturation in oocyte competence