itres) of a special vitrification solution, before storing in liquid nitrogen. This process prevents ice crystals forming, which do so much damage to the structure of the egg. Dr Kuwayama froze 111 eggs, of which 94.5% survived freeze-thawing, 90.5% were fertilised using ICSI (intra-cytoplasmic sperm injection), and 50% of the resulting zygotes were successfully developed for embryo transfer. Twelve pregnancies resulted from 29 embryo transfers (a pregnancy rate of 41.9%, compared with 42.5% using fresh eggs), with an average of 2.3 embryos transferred each time (compared with an average of 1.1 embryos formed from fresh eggs). Eleven healthy babies were born (nine singletons and one pair of twins), while two pregnancies miscarried. The women were aged between 25 and 37.
Dr Kuwayama said: "The conventional slow freeze-thawing method has been used successfully for human embryos in assisted reproduction for two decades, but has been far less successful for oocytes. The post-thaw survival rate for human embryos is about 85-90%. Now, using the Cryotop method, we can achieve post-thaw survival rates for oocytes of 90-95%, making oocyte cryopreservation a real option for women.
"This technology opens up new horizons for medically assisted reproduction in women, enabling them to have the option of having children at a later date by freezing eggs rather than embryos. Moreover, it will help to eliminate the existing time differences in fertility between men and women, whereby women's supplies of eggs decline at a faster rate than men's supplies of sperm."
Dr Chamayou, scientific director of the Unita di Medicina Della Riproduzione, Fondazione HERA, Catania, Italy, told the conference that Italy had banned embryo and zygote freezing in 2004, and any embryos created for IVF, up to a maximum of three, had to be implanted in one transfer. As a consequence of this new law, interest in egg freezing had grown. "Even although oocyte freezing is still considerPage: 1 2 3 4 5 6 Related biology news :1
Source:European Society for Human Reproduction and Embryology
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