Developments in Use of CGH
to Select Frozen Donor Oocytes
By: Steve Masler, CEO Fertility Source Companies
Fertility Source Companies
As the technology for freezing and thawing oocytes has improved, it has been thought that considerable benefit could accrue from the use of the technology to freeze the oocytes of donors for later selection and use by prospective Intended Parents. The thought has been to eliminate much of the cumbersome and costly coordinatio n of the cycles of oocyte donors and those of the Intended Parents. However, the hopes for using egg freezing for that purpose have not become a reality. Now recent research may hasten the time when egg freezing will be more liberally applied to the egg donation process.
Recently published in Fertility and Sterility is an article by Geoff Sher MD, et al, entitled "Oocyte Karyotyping by Comparative Genomic Hybridization Provides a Highly Reliable Method for Selecting “Competent” Embryos, Markedly Improving In Vitro Fertilization Outcome; A Multiphase Study" (1). The article describes a study that first tested the hypothesis that karyotypes from polar body biopsies of oocytes are highly indicative of the karyotypes from polar body biopsies of resultant embryos. Secondly, the study indicates that there were high pregnancy success rates from euploid oocytes, i.e. 82% implantation rate and 74% ongoing pregnancy rate.
The results of the two phases of the study indicate that screening of oocytes by CGH can select those oocytes most suited for fertilization and such selection will result in high pregnancy success rates for the resultant embryos. This conclusion can be applied to the oocyte donation model, via freezing and banking of euploid oocytes for later use by Intended Parents who can select the donor oocytes, knowing that they have already been successfully karyotyped.
It should be understood that in spite of the above, there are still practical factors preventing widespread adaptation of oocyte freezing and banking for oocyte donation.
- Application of CGH to the oocytes is an expensive process.
- It is possible that CGH might also have to be applied to the resultant embryos to validate the oocyte results. This further adds to an expensive process.
- All costs of the oocyte donation process would have to be borne by some organization until frozen and stored oocytes were selected by ultimate Intended Parents. This could represent a prohibitive outlay for most organizations.
- It is still widely considered that fresh oocyte donation results will exceed those provided after the oocyte freezing process.
In spite of the benefits of elimination of concurrent Donor/Intended Parent cycles, future studies providing conclusive proof of vastly superior success rates from oocyte freezing after CGH testing will be required before egg freezing is applied on a widespread basis to egg donation cycles.
References
1. Geoffrey Sher MD, Levent Keskintepe, PhD, Meral Ksekintepe, PhD, Mike Ginsberg, MS, Ghanima Maassarani, Dr. Med. Tahsin Yakut, MD, Volkan Baltaci, MD Dirk Kotzke, MS, and Evrim Unsal, BS, entitled "Oocyte Karyotyping by Comparative Genomic Hybridization Provides a Highly Reliable Method for Selecting “Competent' Embryos, Markedly Improving In Vitro Fertilization Outcome; A Multiphase Study. Fertility and Sterilityâ, 2007.
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