Oocyte diameter as a predictor of fertilization and embryo quality in assisted reproduction cycles.

Objective: To assess the impact of the mean oocyte diameter (MOD) on occurrence of fertilization and embryo quality in assisted reproduction cycles.

Design: Prospective observational study.

Setting: Sector of Human Reproduction of the University Hospital, Faculty of Medicine of Ribeirão Preto, University of São Paulo (HCFMRP-USP).

Patient(s): Thirty-five women undergoing intracytoplasmic sperm injection (ICSI) at the University Hospital of Ribeirão Preto from May to October 2007.

Intervention(s): MOD assessment.

Main Outcome Measure(s): Occurrence of fertilization and qualitative embryo classification on 2nd and 3rd day after ICSI.

Result(s): We divided 160 metaphase II oocytes according to MOD into groups A (MOD below the 25th percentile), B (MOD between 25th and 75th percentile), and C (MOD above the 75th percentile). There was no statistically significant association between MOD and the occurrence of fertilization or the qualitative embryo classification on days 2 and 3. There was no statistically significant difference between groups regarding number of cells or the qualitative embryo classification on days 2 and 3.

Conclusion(s): The MOD of mature oocytes does not seem to be related to the occurrence of fertilization or to the developmental quality of human embryos on days 2 and 3 after ICSI.