Embryo Cryopreservation
Embryo cryopreservation is a procedure carried out when there are good quality embryos that will not be transferred to the patient’s uterus during this treatment cycle.
Embryos are cryopreserved using the vitrification technique. In our laboratory, embryos from the 5th or 6th day of development that are of good quality and have not been transferred are cryopreserved.
About Embryo Cryopreservation
Embryos are cryopreserved using the vitrification technique – a rapid freezing method that uses cryoprotective solutions to protect the embryonic cells from the rapid cooling to which they are subjected. The embryos are cryopreserved in devices called straws. These reeds are stored in containers of liquid nitrogen (-196 o C).
During a cycle of In Vitro Fertilisation (IVF or ICSI), several oocytes are fertilised in order to increase the probability of obtaining embryos with the potential to lead to pregnancy. For this reason, we may obtain more embryos than will be transferred during this cycle.
In other situations, it may not be safe or advantageous to transfer the embryos in the same cycle in which they were created, either because of the risk of ovarian hyperstimulation syndrome, or because of desynchronisation of the endometrium with the phase of the cycle in which the embryos are to be transferred.
In these cases, the embryos can be cryopreserved for use in a subsequent treatment cycle.
In Preimplantation Genetic Diagnosis cycles, it is also necessary to cryopreserve the embryos tested until the results of the genetic tests are obtained.
Embryos can be cryopreserved in the cleavage phase (3rd day of development) or in the blastocyst phase (5th/6th day of development).
Cryopreservation in the cleavage phase is already rare, as blastocyst freezing offers greater guarantees of success. The blastocyst is an embryo which has already demonstrated its capacity for differentiation in the different structures of which it is composed (internal cell mass and trophoectoderm), enabling a more precise morphological classification than the cleavage phase.
The cryopreserved embryos are thawed a few hours before transfer to the patient’s uterus, whose endometrium has already been prepared, either medically or naturally, to receive the embryos.
After thawing, the embryos remain in culture until transfer, their development being carefully monitored to guarantee their survival and quality.
Cryopreservation of embryos by vitrification is a very common technique in Medically Assisted Reproduction laboratories and has good embryo survival and pregnancy rates.
Common questions
Several studies have concluded that embryo cryopreservation does not involve any increased risks and that there is no proven correlation between pregnancy complications or the health of the mother or baby when cryopreserved embryos are used.
Although embryo vitrification is a technique that has been tried and tested in assisted reproduction laboratories, it is not possible to guarantee that the embryo will withstand the freezing and thawing procedures. However, the embryo survival rate is quite high and situations in which an embryo does not survive the procedure are rare. It is important that these techniques are carried out by experienced professionals.
At the beginning of an IVF/ICSI treatment, you will sign a specific informed consent for this treatment in which you will have to express your agreement or not to cryopreserve any surplus embryos resulting from this treatment.
Once cryopreservation has taken place, you will have to sign a new informed consent specific to cryopreservation.
Under current Portuguese law, embryos can remain cryopreserved for a period of 3 years, renewable for a further 3 years.
If you do not wish to transfer your cryopreserved embryos, you may consent to their donation to other recipients of Medically Assisted Reproduction treatments or to their donation to scientific research projects. If you do not consent to either of these, the embryos will be thawed and discarded.
Embryo cryopreservation is a technique that avoids discarding good quality embryos that would not be transferred in the treatment cycle in which they were created. However, the creation of supernumerary embryos is not the aim of IVF/ICSI treatment, so it is not possible to guarantee that embryos will be cryopreserved.
At the CETI, embryo cryopreservation does not entail any additional costs, but a maintenance fee is payable after the first year.
You can consult the CETI price list here.