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What happens to cryopreserved embryos?




Thanks to the advances that have been made in the world of cryobiology and assisted reproduction, embryo banks are now a reality. In the past, it was most common to use more than one embryo in a transfer, resulting in almost no embryos remaining. Nowadays, this practice has taken a 180-degree turn due to the improvement of protocols, vitrification techniques and laboratory conditions in clinics specializing in assisted reproduction. Today we only need an average of two embryos per transfer and as a consequence, we find ourselves with too many surplus embryos, which has caused the centers to find themselves with an excess of cryopreserved embryos.

The first birth worldwide after cryopreservation and thawing of embryos was in 1983, but it was not until 2009 when the vitrification technique began to be used in Spain. However, it was in 2006 when Law 14/2006 was passed, which currently regulates the operation and administration of these banks.

This law (14/2006) states that the use of cryopreserved oocytes and ovarian tissue requires prior authorization from the corresponding health authority and that they may be used whenever medical conditions so permit. Pre-embryos left over from the application of in vitro fertilization (IVF) techniques that are not transferred to the woman in a reproductive cycle may be cryopreserved in banks authorized for this purpose.

This preservation may be prolonged until such time as it is considered by the medical staff, with the favorable opinion of independent specialists outside the corresponding center, that the recipient does not meet the clinically adequate requirements for the practice of the assisted reproduction technique. These pre-embryos can also be donated by the patients themselves to the clinic for reproductive purposes, for other patients who have fertility problems and are unable to produce embryos or for research; this is known as embryo adoption.

The use of these pre-embryos, semen or oocytes will require the corresponding duly accredited informed consent. In the case of pre-embryos, at least every two years, the couple or female progenitor will be asked to renew or modify the previously signed consent. If during two consecutive renewals it is impossible to obtain the signature of consent from the woman or the progenitor partner, the pre-embryos will remain at the disposal of the centers where they are cryopreserved, who may use them for any of the aforementioned purposes, maintaining the established requirements of confidentiality and anonymity, as well as being free of charge and not for profit.

Likewise, the law establishes that assisted reproduction centers that proceed to the cryopreservation of human gametes or pre-embryos must have a insurance or financial guarantee to ensure its solvency to financially compensate couples in the event of an accident affecting their cryopreservation, provided that the procedures and deadlines for renewal of informed consent have been complied with. (Art.11,7 Law 14/2006).

Banked embryos should not remain cryopreserved indefinitely. In the following, we are going to expose the alternatives that exist to be able to use these frozen embryos:

a) Use by the woman herself or her spouse. Law 14/2006 establishes that the maximum age of maintenance is determined by the gynecological aptitude of the patient. In addition, it should be noted that clinics usually set an ethical age limit.

b) Donation for reproductive purposes. According to the law, the maximum age of donors is set at 35 years for women and 50 years for men. In addition, it is determined that they must meet a series of physical and psychological requirements in order to be eligible for donation. Also, the law states that there can be no more than 6 live newborns per donor.

c) Donation for research purposes. In order to be used for this purpose, there must be a project approved by the ethical committees of the center itself, the Ministry of Education and Science and CNRHA (National Committee for Assisted Human Reproduction, also created by this law) and it must meet certain requirements:

– Such research must comply with ethical principles and the applicable legal regime and meet the principles of relevance, feasibility and suitability of the research team and the center where it will be carried out.

– It must be based on a research project authorized by the competent state or regional authority, with a favorable report from the Commission of Guarantees for the Donation and Use of Human Cells and Tissues.

d) The cessation of their conservation without any other use. This only applies once the maximum conservation period established by law has expired.

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