In January 2006, China’s first and the second international case of “triple-frozen” IVF baby was born, and the chromosome test report showed that the body of this “triple-frozen” IVF baby was normal, thus marking another step forward for China’s assisted reproductive medicine technology in the field of reproductive medicine. This signifies that China’s assisted reproductive medicine technology in the field of reproductive medicine has stepped up to a new level. You may have some questions: what is “triple frozen” IVF? Doesn’t freezing cause any damage to the embryos? The “three-frozen” IVF is born after egg freezing, sperm freezing, embryo freezing, and then thawing and transplanting into the mother’s uterus, that is, using the freezing technology to reduce the sperm, egg and embryo from the physiological temperature to a low temperature and storage, and then thawed from the low temperature state to the physiological temperature when needed, because the low temperature can inhibit or stop the cellular metabolism, to maintain its own energy not to be consumed, but the freeze-thawing is not a good way to prevent the embryo from being damaged. energy is not consumed, but freezing and thawing may cause some damage to the cells. Cryopreservation technology has been widely used in the field of assisted reproduction and has become an indispensable part of assisted reproduction technology. Embryo freezing is an extremely crucial step in the implementation of IVF. Couples who wish to realize their dream of having a child through IVF, after following all the targeted treatments in conjunction with the doctor’s step-by-step procedure, of course, aspire for a successful outcome. However, due to various reasons, this may not be possible. In this case, if the patient has to go through the IVF cycle from ovulation induction, fertilization to embryo transfer once or even several times again, it is a physical and psychological torture for the patient, and it also increases a lot of costs, as the medication for ovulation induction accounts for more than half of the whole cost. The clinical application of embryo freezing technology minimizes the physiological, psychological and economic burdens of patients, and helps them to realize their dream of pregnancy through IVF. When multiple embryos are formed in the IVF treatment cycle and good quality embryos are still left after transfer, these embryos can be frozen and preserved. The transfer of too many embryos can be avoided and the occurrence of multiple births can be reduced. Moreover, if the treatment fails in this cycle, the embryos can be thawed and resuscitated and transferred in the subsequent natural cycle, avoiding the need for ovulation and egg retrieval again, and the endocrine environment and receptivity of the uterine lining in the natural cycle are favorable for embryo implantation, which increases the chances of conception once. The use of embryo freezing technology can also prevent the occurrence of severe ovarian hyperstimulation syndrome. When there is a tendency of severe ovarian hyperstimulation syndrome in the IVF treatment cycle, abandoning the transfer of fresh embryos and freezing and preserving the embryos for later transfer can significantly reduce the occurrence of severe ovarian hyperstimulation syndrome. In addition, in special cases (e.g., poor endometrial conditions during ovulation cycles, bleeding, etc., as in the case of mothers of “triple-frozen babies”), embryo implantation may be compromised, and embryos may be frozen and stored until the endometrium has been adequately prepared for the implantation. Frozen embryos also facilitate the screening of embryos for pre-implantation genetic diagnosis. Embryo freezing also facilitates egg donation without requiring synchronization of the donor’s and recipient’s menstrual cycles. Sperm freezing Sperm is easy to collect and easy to detect in terms of number and motility, which provides strong conditions for the freezing of semen and the establishment of sperm banks. In the field of reproduction, sperm freezing technology is mainly used for: ① Infertility treatment, sperm freezing can help couples who are unable to provide usable semen at the right time in the treatment cycle, such as those who have difficulty in semen collection, can take semen in advance and freeze it, and then resuscitate it for use when needed; for those who have little or weak spermatozoa, they can adopt the method of mixing the process after freezing the sperm in several ejaculations separately; in addition, the human sperm bank set up by the freezing technology can also provide qualified sperm for patients with azoospermia, and can also be used to provide sperm for patients with azoospermia. In addition, the human sperm bank established through freezing technology can also provide qualified frozen semen specimens for azoospermia patients. The birth of the “three frozen babies” is because on the day of egg collection, the male semen and testicular biopsy failed to get sperm and finally used the sperm bank sperm. Sperm freezing can be used as a form of fertility reserve. For men who are engaged in jobs that may affect their fertility (e.g., exposure to toxic substances, radiation), for men who are going to undergo surgical treatments that damage fertility (e.g., paratesticular and testicular surgeries), and for men who need to undergo radiation or chemotherapy due to tumors, sperm can be retrieved ahead of time and cryopreserved. In modern society, there are still some people who do not want to have children when they are young due to work or study, etc. Sperm freezing technology can reserve part of the sperm for them to use when they have children in the future. (iii) Promote family planning and eugenics, for example, a portion of semen can be frozen and stored in advance before male vasectomy, so that it can be used in case of requesting to have another child in the future. For couples in which the male partner suffers from a genetic disease or is a carrier of the gene that causes a genetic disease, the semen specimen provided by the sperm bank can prevent the occurrence of hereditary diseases in the next generation. Being able to preserve your healthy and perfect eggs while you are single is a blessing for many women. This is because many women are left with lifelong regrets due to missing out on the best time to have children; or young women with tumors that require radiation and chemotherapy greatly damage their egg cells and even lose their fertility. However, egg cryopreservation is relatively more complicated. Because women can only produce a few eggs at a time, and because human oocytes are large in size, the delicate cytoplasmic structure and spindle are easily damaged by freezing, egg freezing is much more demanding than sperm freezing and embryo freezing. Current technology for embryo and sperm freezing is relatively mature, and through improvements in cryoprotectants, selection of frozen embryos, and improved freezing and resuscitation techniques, it is possible to obtain the same implantation and pregnancy rates with frozen embryos as with fresh embryos. Whereas spermatozoa are easy to obtain and in large quantities, the number of remaining spermatozoa during cryo-resuscitation is still large enough to satisfy the need for treatment even if the percentage of spermatozoa deaths is high, but in the case of semen specimens with oligozoospermia, the death of spermatozoa during cryopreservation will have a greater impact on spermatozoa function, and the addition of cryoprotectant can prevent and minimize the damages caused during cryopreservation and resuscitation, thus ensuring that the sperm have a high survival rate even after resuscitation. However, egg freezing is a cutting-edge technology in the field of assisted reproductive medicine, and the most difficult aspect of “egg freezing” lies in how to utilize high technology to thaw frozen eggs and restore them to the proper temperature for fertilization without destroying their original structure. Although there are successful examples, this technology has not yet been maturely applied in the clinic, and egg freezing and preservation technology is still a worldwide problem.