Sperm freezing may be needed if the husband is about to undergo radiation or chemotherapy for cancer, or needs a surgical procedure to retrieve sperm. It can also be useful if the male partner is afraid that on the day of your procedure he may be too nervous to provide a specimen. Sperms are hardy survivors and most of them will tolerate the process of freezing without damage.
Embryo freezing is useful in situations where an excess of embryos has been produced in an IVF or ICSI cycle and there are left-over embryos even after the selected ones are transferred. Embryo freezing can also be useful when a cycle may have to be cancelled due to the risk of ovarian hyperstimulation. Embryos do not tolerate freezing to the same extent as sperms. The pregnancy rates with frozen-thawed embryos is lower (15 to 20%) as compared to fresh embryo transfers (35 to 40%).
Cryopreservation is a technically demanding process. The material to be preserved is first protected with a medium (chemicals which prevent sperm and embryo damage) called cryoprotectant. After being correctly labeled and identified, they are placed in metal tubes and stored in tanks of liquid nitrogen where the temperature is reduced gradually to – (negative) 196 degree Celsius. When the sperm or embryo has to be used, it is gradually thawed and brought to body temperature.
At the present time, technology for freezing extra eggs is experimental.