Errors at mitotic segregation early in oogenesis and at first meiotic division in oocytes from donor females: comparative genomic hybridization analyses in metaphase II oocytes and their first polar body.

The aim of this work is to analyze, using the comparative genomic hybridization technique, the frequencies and the mechanisms involved in the production of aneuploidy events in donor oocytes. The results showed that 32.1% of them were aneuploid, with 51.7% of those originating from first meiotic division errors and 48.3% from the presence of aneuploid oogonium.

Comments on oocyte cryopreservation.

Recently, Robert Winston stated publicly that freezing human oocytes could cause irreparable harm to future generations. In this paper, this affirmation is refuted with arguments and facts. With regard to the low efficacy of the oocyte freezing technique, data are provided on the number of frozen oocytes required to achieve one pregnancy: 100, 17 and 25 in three different papers, compared with 50 fresh oocytes in another. Two recent articles are cited. One shows similar results (pregnancy/cycle) when using frozen oocytes and frozen embryos (17.2 and 18.7% respectively). The other reported birth rates with fresh oocytes (57.9%), frozen embryos (52.9%) and frozen oocytes (45.8%). The legal situation with regard to freezing oocytes in Spain is described, as is the legal uncertainty experienced by the CEFER Reproduction Institute when it began freezing human oocytes for use in assisted reproduction.