Infertility is medically defined as the absence of a successful pregnancy after one year of normal sexual intercourse without the use of any contraception. There are two main types of infertility: primary infertility and secondary infertility. Primary infertility is defined as never having conceived; secondary infertility is defined as having been pregnant and then becoming infertile. According to this strict definition, infertility is a common problem that affects approximately at least 10% to 15% of couples of reproductive age. Especially with a population base of 1.3 billion people like ours, the number of infertile couples is quite alarming. The causes of infertility are divided into male infertility and female infertility. Common causes Ovulation disorders, semen abnormalities, fallopian tube abnormalities, unexplained infertility, endometriosis, immunological infertility, etc. A large proportion of infertile couples will conceive naturally after allopathic medical intervention and guidance, which is of course a happy ending for all. However, there are many couples who are not so fortunate and who have sought medical help but have failed to conceive naturally. Finally, they resort to assisted reproduction techniques, the main methods being artificial insemination (AI) and in vitro fertilization-embryo transfer (IVF-ET or ICSI) (i.e. IVF), with a maximum pregnancy success rate of about 40 to 50 percent. In IVF-ET, due to the use of ovulation promotion, the follicles recovered in one cycle and the embryos developed by fertilization will be left over after transfer and need to be frozen for storage, so that if the transfer fails, they can be transferred in the next natural cycle or HRT cycle to improve the pregnancy rate in one egg retrieval. In addition, if a patient has ovarian stimulation syndrome caused by ovulation promotion, the embryos can be frozen and stored for later transfer to prevent aggravation of the pregnancy. Frozeneggs The mechanism of embryo freezing is that ultra-low temperature inhibits cell metabolism and preserves life in a dormant state, i.e. “frozen life”. The preservation temperature is -196℃, and the preservation device is a liquid nitrogen tank with liquid nitrogen as the cooling source. Cryopreservation of embryos is the only proven method in the world to preserve reproductive function. Theoretically, it can be preserved for a long time, and in some fertility centers in China, there are embryos that have been frozen for more than 10 years, and after recovery and optimization, they can be transferred to normal pregnancy without any problem. But in fact, nowadays, reproductive medicine professionals do not advocate freezing embryos for too long, let alone for similar somewhat commercialized hype. For example, the city of Shanghai stipulates that embryos in Shanghai can only be frozen for a maximum of five years. That is, professionals would advise patients not to freeze their embryos for too long, and to recover them for optimal transfer if they want to have a second child within five years. Of course, this is not particularly strict, as to how long the embryos are frozen and preserved, there are no large samples of data available. From the point of view of pregnancy alone, the patient has a frozen spare embryo, which can be preserved and can become pregnant without any problem, but from the point of view of long-term effects, there are no large samples of data, so it is not easy to say. Although assisted reproductive technology is developing rapidly and bringing benefits to millions of infertile families all over the world, professionals still recommend to try to get pregnant naturally. However, professionals still recommend that it is best to try to conceive naturally and that assisted reproduction is only the last stop in the treatment of infertility.