Reliability of comparative genomic hybridization to detect chromosome abnormalities in first polar bodies and metaphase II oocytes.

BACKGROUND: Preimplantation Genetic Diagnosis (PGD) using FISH to analyze up to nine chromosomes to discard chromosomally abnormal embryos has resulted in an increase of pregnancy rates in certain groups of patients. However, the number of chromosomes that can be analyzed is a clear limitation. We evaluate the reliability of using comparative genomic hybridization (CGH) to detect the whole set of chromosomes, as an alternative to PGD using FISH.

METHODS AND RESULTS: We have analysed by CGH both, first polar bodies (1PBs) and metaphase II (MII) oocytes from 30 oocytes donated by 24 women. The aneuploidy rate was 48%. Considering two maternal age groups, a higher number of chromosome abnormalities were detected in the older group of oocytes (23% versus 75%, P < 0.02). About 33% of the 1PB-MII oocyte doublets diagnosed as aneuploid by CGH would have been misdiagnosed as normal if FISH with nine chromosome probes had been used.

CONCLUSION: We demonstrate the reliability of 1PB analysis by CGH, to detect almost any chromosome abnormality in oocytes as well as unbalanced segregations of maternal translocations in a time frame compatible with regular in vitro fertilization (IVF). The selection of euploid oocytes could help to increase implantation and pregnancy rates of patients undergoing IVF treatment.