Cryopreservation (from Greek κρύος — cold and Latin
conservo — preserve) — low-temperature storage of living biological objects with the possibility of restoring their biological functions after thawing.
What cryopreservation (freezing) programs are used in assisted reproductive technologies?
Medical technologies allow not only to perform manipulations with gametes and embryos,
but also to carry out their cryopreservation.
For a long period of time, they can remain in a frozen state and subsequently be used in reproductive technologies. It should be noted that the cryopreservation of gametes finds its support in international ethical documents. For example, in the Statement on Artificial Insemination and Transplantation of Embryos, adopted by the 39th World Medical Assembly (Madrid, Spain, October 1987), it is specifically indicated: "If an excess of oocytes occurs during IVF,
which will not be immediately used for infertility treatment, their further fate should be determined jointly with the donors.
Surplus eggs may be:
a) destroyed;
b) subjected to cryopreservation for frozen storage;
c) fertilized and subjected to cryopreservation.
Currently, the following programs are in use:
— cryopreservation (freezing) of sperm,
— cryopreservation (freezing) of oocytes (eggs),
— cryopreservation (freezing) of testicular or ovarian tissue (tissue of male or female gonads),
— cryopreservation (freezing) of embryos.
What are the legal aspects of cryopreservation and storage of germ cells and embryos in Ukraine?
Cryopreservation of biomaterial in assisted reproductive technology programs is regulated by the order of the Ministry of Health of Ukraine No. 771:
"For the preservation of donor sperm,
oocytes,
embryos, and biological material
obtained from the testicle or its appendage,
Cryopreservation of them is carried out based on the Patients' Statement on Cryopreservation of Sperm (Oocytes) Embryos and the Donors' Statement on Cryopreservation of Sperm, Oocytes, Embryos, and Biological Material obtained from the testis or its appendage.
Cryopreservation of sperm, oocytes, embryos, and biological material obtained from the testis, its appendage, ovarian tissue is performed using programmable cryogenic equipment or vitrification according to the techniques,
рекомендованным фирмами — производителями патентованных питательных сред при наличии свидетельства о регистрации.
In case of need, at the request of patients, the cryopreservation period can be extended based on a separate application from donors.
An embryology specialist conducts the freezing and thawing procedures of donor material,
assesses the quality before and after cryopreservation,
ensures the necessary storage conditions and usage of biomaterial,
recommended and tested protocols of nutrient medium manufacturers.
How long can frozen embryos be stored,
and what is a cryo-storage facility?
Theoretically,
if storage conditions are stable,
the duration is not limited.
However, there is a known case of a successful pregnancy after the transfer of embryos
that had been stored in liquid nitrogen for 12 years.
Initially, the declaration for cryopreservation is filled out for 1 year,
and then further as per the patient's wish.
In general terms,
криохранилище — это помещение с сосудами Дьюара: нечто вроде гигантского металлического термоса, заполненного жидким азотом. В нем есть специальные ячейки, в которых находятся соломинки с замороженными эмбрионами.
Как могут быть использованы избыточные половые клетки или эмбрионы?
В случае заявления от пациента на криоконсервацию биоматериала последний может быть использован в дальнейшем для проведения криоциклов у данных пациентов либо у других пациентов, нуждающихся в донорских половых клетках или эмбрионах,
The possibility of a second option is also discussed in the statement.
If the patient does not write a cryopreservation statement, their excess biomaterial is disposed of.
What are the indications and benefits of cryopreservation (freezing) of gametes and embryos?
Indications for cryopreservation of oocytes and sperm:
- freezing donor sperm,
- absence of a sexual partner on the intended day of embryo transfer (sperm cryopreservation is carried out in advance),
Indications for embryo cryopreservation:
- high risk of developing severe ovarian hyperstimulation syndrome when embryo transfer is canceled,
- poor endometrial quality for the implantation of transferred embryos,
- "excess" embryos after transfer.
What is the survival rate of embryos after cryopreservation?
Currently, the survival rate of embryos after freezing ranges from 22 to 70% depending on the cryopreservation method.
What embryo cryopreservation method is used at the reproductive medicine clinic "Genesis-Dnepr"?
The process of embryo cryopreservation is carried out using a programmed freezer or vitrification (rapid freezing).
Программа криоконсервации определяется стадией развития эмбриона и видом криопротектора. Хранение замороженных эмбрионов осуществляется в специальных маркированных пластиковых соломинках, помещенных в жидкий азот. Преимущество метода витрификации в том, что заморозка данным методом более щадящая и выживаемость эмбрионов после разморозки составляет 50-70%.
What are the advantages of cryopreserving surplus embryos?
The advantages are obvious:
- the transfer of thawed embryos can be carried out in the first cycle after an unsuccessful attempt,
- the so-called cryotransfer is performed in a natural cycle without superovulation stimulation programs and ovarian puncture, thereby reducing the frequency of complications and decreasing the cost,
- after thawing, more viable embryos "survive," increasing the likelihood of pregnancy and reducing the risk of miscarriage of the given pregnancy.
What is the frequency of pregnancy after "cryotransfer"?
The pregnancy rate after the transfer of thawed embryos ranges from 10-15% to 40%.
How does the freezing of gametes and embryos affect the future development of the child?
The cryopreservation program (freezing) of embryos has been used in assisted reproductive technologies since 1982.
The first child born after the transfer of thawed embryos was born in 1984.
Children
born after a cryopreservation protocol,
do not differ in their indicators and development from those after classical IVF and spontaneous pregnancies.
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