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Embryo cryopreservation is the instant freezing of embryos using liquid nitrogen at a temperature of -196 degrees Celsius. Frozen embryos can be stored for several years, while their vital activity is not disturbed. Embryos are frozen for the purpose of their further use for the IVF procedure. Experts recommend cryopreservation of embryos if there are risks of unsuccessful IVF procedures, receiving a large number of embryos during the preparation for IVF, as well as when participating in a surrogate motherhood program. each pair.
Advantages and disadvantages of the procedure
Cryopreservation of samples for further transplantation has several advantages. Among them is the opportunity to donate a sample as a donor for other infertile couples, the conception of a child several years later, after suffering serious illnesses. The procedure prevents ovarian hyperstimulation syndrome, saves money on the purchase of expensive drugs.
In addition, there is no need to re-stimulate the ovaries, therefore, the load on the female body is reduced and the chances of pregnancy remain high.
But it is worth noting the disadvantage – this is the likelihood of losing some of the materials during the freezing and thawing procedure. It is for this reason that it is imperative to agree on the risks with the doctor and prepare as many samples as possible for freezing.
Procedure Algorithm
Various fertility centers practice cryopreservation procedures at different stages of their development: blastocysts, eight-cell or four-cell, a fertilized egg. The main condition is the good quality of the frozen material to increase the percentage of embryo survival after thawing.
At the very beginning, the material is placed in a special cryoprotective medium with the addition of special preparations that will protect cells from possible damage during the freezing period. With the help of these substances, the likelihood of the formation of ice crystals in the middle of the embryos themselves is prevented, they turn the cytoplasm of cells into a gel-like state and, in the process of defrosting, their properties are completely restored.
After the preparatory procedures:
- samples are placed in special containers – small plastic tubes with appropriate markings;
- 4-5 pieces are placed in each container;
- finished tubes are placed in a cryobank;
- the cooling procedure starts (slow or super fast).
Properly frozen samples in a cryobank are stored for as long as necessary – from several months to tens of years, but payment for storage is made by an advance system. The maximum shelf life is 55 years.
At the end of the paid storage period, the couple is asked about their future fate: disposal, extension of the shelf life, fertilization, use for scientific purposes, permission to use as a donor sample for another couple.
In order to thaw the samples, the containers are removed from liquid nitrogen, the thawing process takes place at room temperature, after which the embryos are transferred to a favorable environment. The placement of the material in the uterus is carried out during the period when the samples will be in the blastocyst stage. The transfer of frozen materials can be carried out in a natural cycle, in a stimulated cycle, or in a cycle with special hormonal therapy.
The type of cycle is determined directly by the doctor, taking into account the state of health of the patient before replanting.
Approximately 50 percent of patients after the first IVF procedure can freeze additional materials as a reinsurance (in case the replanting is not successful). The procedure for freezing and storing ready-made embryos is much cheaper than a new IVF procedure from the very beginning.
Influence of cryopreservation on IVF outcome and further development of children
It has been proven that cryopreservation does not affect the development of the embryo and the formation of the child, but they can be damaged during the period of thawing or freezing. It is worth noting that emergency freezing is much more effective, since after it the survival rate of samples is 98 percent, and with slow freezing, about 50 percent survive. It is for this reason that it is recommended to clarify the method of freezing in the clinic. The result of embryo transfer and further pregnancy depends not only on the embryo, but also on other factors: the number of transferred embryos, the correct medical support, the age of the woman.
Children who are born after IVF with cryo-frozen embryos are no different from ordinary children.
It should be understood that before carrying out the fertilization procedure of the resulting egg, thorough examinations of both the egg and sperm at the time of pathologies are carried out. Ready embryos are also checked for genetic failures. Therefore, the occurrence and development of pathology in a child is equated to a minimum. Moreover, provided that the woman is completely healthy, the implanted embryo takes root, and neither pregnancy, nor childbirth, nor the further development of the child will be problematic. It is only important to discuss how many embryos will be transferred at the same time, so that later one or more will not have to be removed. There are cases when all three out of three transplants take root, and not every family is ready for the birth of three children at once.
The choice of a clinic should be approached as responsibly as possible, study all the conditions, all the rules, carefully read the contract, and only after that proceed with the procedure. Remember, the success of pregnancy and the health of your child will depend on the quality of the clinic in the future.