The cytogenetic constitution of embryos derived from immature (metaphase I) oocytes obtained after ovarian hyperstimulation.

Objective: To examine the chromosomal content of embryos resulting from metaphase I (MI) oocytes obtained after ovarian hyperstimulation for IVF.

Design: Prospective cohort study.

Setting: University-based IVF Center, Assaf Harofeh Medical Center, Tel Aviv University, Israel.

Patient(s): One hundred fifty women undergoing assisted reproduction technique (ART).

Intervention(s): Intracytoplasmic sperm injection (ICSI) was performed in MI oocytes that were retrieved after ovarian stimulation. A portion of these oocytes extruded their polar body (rescued in vitro-matured metaphase II [IVM-MII]) after different incubation periods and the remainder did not (arrested MI oocytes). Fluorescence in situ hybridization was performed using probes for chromosomes X, Y, 18.

Main Outcome Measure(s): Fertilization rate, number of blastomeres, and embryo euploidy.

Result(s): Embryos from rescued IVM-MII oocytes showed significantly higher fertilization rates and more blastomeres per embryo compared with those from arrested MI oocytes (58.5% vs. 43.9% and 5.7 vs. 5.0, respectively). The chromosomal analysis of these embryos revealed a high rate of aberrations (80.6%), mainly complex mosaics. This rate was elevated in embryos from arrested IVM oocytes (97.2%), and after longer incubation periods. No chromosomally normal embryos were found after 24 hours of incubation of their corresponding oocytes.

Conclusion(s): Embryos originating from MI oocytes have a high rate of chromosomal aneuploidy, and their replacement should be reconsidered.