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| Resources > Newsletters > Preserving Female Fertility |
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| Preserving Female Fertility |
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| Cryopreservation of human sperm has been available for decades, allowing men who would otherwise become sterile due to radiation, chemotherapy or surgery to store their sperm for future use. Women may also confront these issues, and consequently much scientific research has also been devoted to attempts at cryopreser-vation of human oocytes. Unfortunately, the techniques involved in sperm cryopreservation have not been adaptable to eggs. This is because the small size and relatively low water content of sperm makes it easy to freeze and store without much damage. In contrast, the oocyte is a large cell with high water content. As such, it is prone to ice crystal formation. These crystals may damage the internal structures of the egg, in particular the zona pellucida, cortical granules, and micro-tubules. Prevention of ice crystal formation has remained a formidable challenge. |
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| Unlike the unfertilized oocyte, fertilized oocytes – embryos – have been successfully cryopreserved, thawed and used to establish pregnancies for over two decades. Since first described in 1983, thousands of healthy babies have been born using this technology. Still, there remains a large number of women for whom embryo cryopreservation has little usefulness. As is well known, a variety of social factors has led many women in their mid to late thirties and beyond to postpone childbearing. Many of them have not chosen a partner, and consider using donor sperm simply to fertilize and then store their embryos an unpalatable option. Still, when they are finally |
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| ready, they may have limited reproductive options because of a decline in their ovarian reserve. It would be best for such women to avail themselves, if possible, of a way of protecting their future fertility. |
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| Within the last several years there have been improvements in culture media, cryoprotectants (“antifreeze agents”) and programmable freezers used for oocyte cryopreservation. Investigators now report encouraging results. To date, over 100 healthy babies have been born worldwide as a result of this technology. |
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| Current techniques utilize what is known as the “slow freezing protocol.” It is estimated that, using this protocol, 80% of eggs survive the freeze and thaw process and yield a pregnancy rate as high as 20%. These results are expected to improve as more focused attention is directed towards perfecting the method. Other touted options, such as ovarian tissue cyropreservation followed by re-transplantation, remain unproven and without any verifiable viable pregnancies to date. |
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| At GENESIS, we offer the “slow freeze protocol” to women who wish to preserve their eggs. Women who anticipate losing normal ovarian function due to planned surgery, radiation or chemotherapy for a non-estrogen sensitive cancer or who, for social reasons, anticipate delaying childbearing into or beyond their late thirties would be wise to thoroughly investigate the option of oocyte freezing. |
| July 2005 |
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