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Embryo freezing

Embryo freezing takes place when the number of good quality embryos exceeds the number of embryos to be transferred into the uterus in a cycle of Invitro Fertilization. These cases become more frequent with the current improvement of embryo cultures in IVF treatment cycles. These frozen embryos can be used in a new subsequent attempt known as cryotransfer.

Freezing through vitrification allows embryos to be kept intact for a long. Their implantation capacity is thus unaffected as long as they overcome the freezing-defreezing process successfully. The risk of abortion or embryo malformation is not increased in the transfer of cryopreserved embryos.

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Frozen embryos

Embryos can be frozen at different stages along their development, for instance, on day 2, 3, 4, 5 and 6 of development as convenient in each case.

Embryo freezing is produced with the use of cryo-protectant agents (molecules that protect the cellular membranes of the embryos from the low temperatures to which they are exposed during the freezing process). Once frozen, the embryos are carefully identified and kept in Embryo Banks. These banks are placed in recipients containing liquid nitrogen at a temperature of -196ºC which allows their viability to be maintained for years.

Embryo law

According to the Spanish law on Human Assisted Reproduction Techniques, Law 14/2006, the embryos can be available for the couple all through the woman’s fertile life. This law outlines four options regulating the possible uses of the cryopreserved embryos:

  • Use by the couple themselves (available until the woman’s reproductive limit)
  • Donation to other women or couples with reproductive goals
  • Donation with research purposes
  • Suspension of storage wih no further use (applicable only at the end of the woman’s reproductive life).

The use of the embryos for any of these options requires authorization by the woman or couple formalized in a signed informed consent. This consent can be modified at any given time prior to its use.

To ensure the woman’s or couple’s responsibility for these embryos, the law establishes that the Center shall request the annual renewal of the consents about the state of their embryos. If over two consecutive renewals it proved impossible to obtain the signature of the corresponding consent and the actions taken to obtain such renewal without response can be demonstrated by formal notice, the embryos will remain at the disposal of the Centre that keeps them frozen. The Centre will have the power to allocate them at its discretion to any of the uses mentioned whilst maintaining the confidentiality, anonymity and non for profit requirements.

Embryo thawing - Cryotransfer

Thawing is the process that involves a change in embryo temperature from -196°C (the freezing temperature) to 37°C where they should resume their metabolic activity and reactivate their fertile potential. Specific culture mediums are used to protect the embryo from the increased temperature.

Depending on the moment when the embryos were frozen and the number of embryos available, thawing takes place on the day of the scheduled transfer or some days before, in which case the embryos are left in culture during 2-3 days to observe the capacity to resume the cellular division process in each embryo.

Nowadays, with the use of the freezing technique called vitrification, around 85-95% of the frozen embryos survive the freezing-thawing process successfully.

For the transfer of frozen embryos, the patient does not need to go through the whole process of ovarian stimulation and follicular puncture as the endometriun can be ready and receptive for the implantation of the thawed embryos with a very simple course of medication or even with her own natural menstrual cycle.

Embryo Adoption Program

What is the Embryo Adoption Program?

This program exists solely and exclusively thanks to the solidarity and altruism of couples who, after undergoing Ivf treatment, donate their embryos to give other couples the opportunity to become parents.

Who donates the embryos?

When a couple decides they have ended their reproductive project, they can recourse to Option B of the Spanish Reproductive Law 14/2006 about the destination of the surplus embryos resulting from IVF (Invitro Fertilization treatment). The couples who donate their embryos must be formed by a woman aged 18 - 35 and a man aged 18 – 50 at the moment of embryo freezing. Additionally, subsequent serology testing is carried out in order to prove the seronegativity of the frozen embryos. Once the donation consents are signed, the embryos enter the Embryo Bank at the Centre and the Center assigns them to the recipient couples or women.

Who can receive the embryos?

Any woman or couple in need of receiving eggs or sperm to become parents. Embryo adoption can take place as long as there are embryos available at the Embryo Bank.

How are the embryos assigned?

The system designed for embryo assignation to the receiving couples takes into account the following aspects: phenotypical similarity, blood type and Rh factor, geographical area, etc.

How is the treatment performed?

This procedure can be carried out in two visits.

In the first visit, the female health is assessed through physical and psychologic examination, gynaecological study and an ultrasound scan. Additionally, a mock catheter test is performed (i.e. an embryo transfer is simulated). Then, the endometrial preparation plan is explained and the embryos are assigned.

In the second visit, the embryos defrozen some hours in advance are transferred.

Program results

Success rates for an embryo adoption program are the same as for a frozen embryo transfer, which may reach up to 50% depending on the quality of the frozen embryos.

Is it necessary to conduct adoption proceedings?

No, it isn’t. The sole signature of the embryo adoption consents suffices to determine that the children born as a result of this technique are offspring of the recipient woman or couple.