Cryopreservation of oocytes, also known as "oocyte cryopreservation", is just like a popular star on the Internet being "frozen", using technical means to "freeze" eggs to achieve the purpose of "preservation".
At present, "vitrification" technology is mostly used for eggs. Its basic principle is that high concentration cryoprotectant solidifies at ultra-low temperature to form irregular vitrified solid, which retains the normal distribution of molecules and ions in liquid state, so it can play a protective role when cells vitrify. After the preserved cells were dehydrated to a certain degree in cryoprotectant solution, the endogenous cytoplasmic macromolecules such as protein and cryoprotectant infiltrated into the cells were concentrated, so that the cells were protected in severe and rapid cooling.
At present, "oocyte cryopreservation" belongs to the category of assisted reproductive technology. Our country's laws clearly stipulate that couples with "three certificates" (marriage certificate, identity card and birth certificate) and suffering from infertility can receive assisted reproductive technology diagnosis and treatment. However, assisted reproductive technology has stricter regulations on cryopreservation of oocytes, and it has not been approved as oocyte cryopreservation or embryo for unmarried women or couples with normal fertility in China. In China, oocyte cryopreservation is only applicable to the following two situations: First, due to various reasons, on the day when infertile women take eggs through assisted reproductive technology, if the man fails to provide fresh sperm or frozen sperm in time and refuses to use donor sperm as IVF, the eggs will be completely or partially frozen; Secondly, because chemotherapy has a very bad influence on ovaries and eggs, women with malignant tumors can go to oocyte cryopreservation before receiving high-dose radiotherapy and chemotherapy to help them realize their desire to be mothers at an appropriate time.
However, with the increase of women's age, the pregnancy rate will drop significantly. The pregnancy rate over 44 years old is very low, and the pregnancy rate is the highest among women aged 25 -35. In today's society, more and more women are working hard in the workplace, and the childbearing age is constantly delayed. Therefore, many young or divorced women who don't want to have children for the time being also hope to help them realize their desire to be mothers at an appropriate time through oocyte cryopreservation's technology. Due to the restriction of domestic laws, these needy women usually use overseas medical treatment to achieve their own purpose in oocyte cryopreservation.
However, at present, according to domestic and foreign laws, there are at least five kinds of people who are not suitable for oocyte cryopreservation:
1, women over 35 years old: At the age of 35, the ovarian reserve function has obviously decreased, and oocyte cryopreservation is of little significance at this time;
2. Women with premature ovarian failure due to autoimmune diseases, chromosomes, tumors, infections and other factors;
3. Women who have suffered ovarian damage due to high-dose whole-body radiotherapy and chemotherapy for tumors or repeated surgical treatment for severe and recurrent ovarian cysts;
4. Adolescent patients whose application of other freezing methods is ineffective;
5, sexually transmitted diseases: most patients with sexually transmitted diseases suffer from pelvic inflammatory disease, and the function of female fallopian tubes is destroyed, which greatly reduces the vitality of eggs.
No matter where you are and for what purpose, you need to know the following facts about egg freezing.
1. Can oocyte cryopreservation form normal embryos?
The answer is yes. Although the cryopreservation process of oocytes may be limited by technology or damaged by refrigerants, the frozen eggs can still be accepted to develop into babies after "awakening". Because frozen eggs have to go through the process of frozen resuscitation, if the temperature is not properly controlled or the cryoprotectant itself is toxic, it will do harm to the eggs, and resuscitation is another major difficulty in oocyte cryopreservation. After the low-temperature egg returns to normal temperature, the chromosomes will begin to rearrange. At this time, embryo chromosome abnormality is prone to occur, and there is a risk of abnormal egg structure after resuscitation, and subsequent fertilization and development cannot be completed. But for women who need egg freezing, these can't stop egg freezing, and assisted reproductive technology is still improving.
At present, it is reported that the longest freezing time of eggs can reach 5- 10 years, which means that if the eggs are frozen, women can keep the eggs intact until 5- 10 years later.
2. Will oocyte cryopreservation affect normal pregnancy?
Numerous studies have shown that egg freezing combined with other assisted reproductive technologies can make women get a certain pregnancy rate, with an average pregnancy rate of 34.82%. Although the pregnancy rate is lower than that of fresh unfrozen eggs, the spontaneous abortion rate has not increased.
3. Can oocyte cryopreservation guarantee the success of childbearing in the future?
Importantly, cryopreservation of oocytes does not guarantee that you will have children, but it provides a reliable insurance scheme. For example, you are pregnant 1~2 months, but you are not pregnant. Cryopreservation of oocytes can improve its success rate. When you are going to use cryopreservation of oocytes to give birth to new life, you must complete several steps before pregnancy: thawing eggs, completing fertilization and implanting eggs, all of which you are happy and hope to happen. These steps are likely to fail, and the doctor won't know the result until everything is successfully completed.
4. How much does it cost to freeze eggs?
The cost of egg freezing is about 10000 yuan in the whole process of ovulation induction and pre-inspection in China. Oocytes are cryopreserved in a liquid nitrogen tank at-196℃, and the storage cost does not exceed 3600 yuan per year.
Overseas oocyte cryopreservation needs $ 10000~ 12000 as a whole, and the cost of storing eggs is $800 every year.
5. Compared with frozen embryos, who is more secure for cryopreservation of oocytes?