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Cryopreservation of Embryos
Relevant information about Cryopreservation of Embryos.Currently, there are several procedures in the reproductive assisted fertilization field. Some of them are more common than others. But all of them seek a unique goal: conceiving a life. In this case, during the Cryopreservation of Embryos procedure, the egg recovery is guided under ultrasound, and afterwards the fertilization is carried out. While doing this procedure, it happens that a surplus of embryos appears, followed by a group for transfer to the uterus. In that case, the embryos which have good quality may be considered for the storage. The embryos can be frozen at different stages of the preimplantation. In general, the stage chosen to cryopreserve is the blastocyst period. There are other cases, in which all embryos are frozen without a fresh transfer, after the egg collection at what is called the one-cell stage.
And not only exist many different kind of procedures for reproductive assisted fertilization, but also there are several steps involved in the Cryopreservation of Embryos procedure itself. The ones related to controlling the rate of freezing use the cool embryos in what is denominated as cryoprotectant fluid down to -196°C. At that temperature, the sample or embryo is placed in containers of liquid nitrogen, with the correspondent label. In order to avoid any confusion when carrying out the Cryopreservation of Embryos procedure, the labels are stored in different file systems, so that cryopreserved embryos keep safe for their owners. Furthermore, when the time of performing the procedure with embryos stored comes, the available identifiers of samples must match and be confirmed before continuing. Actually, in every stage of the procedure there are many clear and particular safety measures, as to preserve the conditions and environment of every family. Then, the most complicated aspect of the following procedure is to dilute very carefully the cryoprotectant fluid. That way, a controlled increase and development in vitro is possible. The next step is to assess the embryo for cryodamage, in order to establish if it has the conditions to be transferred. According to numerous previous studies in the field, if the embryo survives a 50% or more with its original characteristics, then it should be replaced. It is a fact that not all couples that decide to have an in vitro fertilization, would need to go through an embryo freezing. The reason for this is that not everybody will count with a large number of non-transferred embryos to be used for the procedure. In general, most of the couples freeze one or two embryos, and in that case all of them are thawed and it is replaced any of the embryos that survive. There is also the possibility of not having any embryo surviving, so in those cases, the transfer is not possible. On the other hand, when there are a lot of embryos suitable to be used in a transfer, extra embryos which count with a good quality may be frozen once again to be used in the future. But there are other important aspects to have into account at this stage of the procedure. The woman, who is undergoing the treatment, will be indicated by her doctor to take estrogen and progesterone, so that she can reach the appropriate endometrial wall to make a success embryo transfer. Even after the transfer is done, the patient will need to continue taking estrogen and progesterone every day for about seven to eight weeks during pregnancy or until she obtains a negative pregnancy test.
Among the advantages of the Cryopreservation of Embryos procedure, stated by specialists, there are several to have into account. First of all, the reduction of any danger is much higher when cryopreservation of embryos exceeds the suggested number for a successful transfer. At the same time, there is a possibility of a lower number of stimulated ovary drug treatment cycles, which are usually demanded to keep pregnancy. And the most common risk, about which every couple is worried, is the loss of embryos to cryoinjury. In case something like that occurs, embryos in good condition may die, due to freezing techniques. Approximated figures show that the embryos lost to cryoinjury can vary from 25-50% of the ones cryostored. And among the consults more frequently made by the couples, there are the possible risks of defects in babies conceived. However, the investigations have stated that there is not a significant increase of defects, in comparison regular pregnancies.
The cryopreservation of embryos procedure started almost by chance. It was by accident, during a cryopreservation of fowl sperm in 1948, when investigators discovered the advantages of this new technique. The mistake occurred due to the investigators confused while labeling there work, and ended up using glycerol instead of other substance. After that marvelous discovery, many advantages have been seen to protect the cells or tissues during the freezing process of embryos. So from that amazing moment on, embryos have been wonderfully thawed after cryopreservation, for over fifteen. As regards pregnancies rates as a result of cryopreservation of embryos procedure, there have been thousands of them notified for over a decade. Actually, the first pregnancy reported from a frozen and thawed human embryo was in 1983, while a baby born as a result of it was notified in 1984. According to figures correspondent to the assisted reproductive technology in the United States, almost 100.000 cases were registered in 2000, which means around 16% of the techniques made.
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