Freezing: An Excellent Option for Planned Pregnancy.

Cell freezing is the technique of preserving cells by freezing, to keep them dormant for a longer period of time. Freezing ensures longevity, something that is unattainable by any other means at present. This has encouraged scientists to pursue this technique for more than a century, and today it is a reality. Freezing suspends all biological activity and stores the cells in the same state for an indefinite period – it is basically a form of immortality. The common tissues that are frozen now-a-days are bone marrow, blood cells, embryos, sperm cells, and eggs.

Fertility as a serious subject has come a long way and has gotten more complex than ever. Currently, cryopreservation is one of the core practices. Ever since 1986, healthy pregnancies are being achieved from cryopreserved cells. Cryopreservation is an important part of advanced infertility treatments. The main advantage of freezing is that it gives us the opportunity to preserve the cells intact for a long period of time.

Who Should Consider Freezing as An Option in Infertility?

It is known that, out of any other parameters age is the most important determinant of the capability to achieve pregnancy. Commonly referred to as the biological clock, there is a timeline for having children. Even though fertility doesn’t end sharply at 35 years as commonly believe, it is neither a random myth. Gradually, fertility will definitely go down with age, so will the quality of embryos formed from aged eggs. This is the reason why single or unmarried women get worried about the passing of time and about the health of future kids, and opt to freeze their eggs during their prime age. Until recently, career-oriented women who are not psychologically ready to start a family in their 20’s and 30’s were forced to decide between career or family.

Increasingly, in Western countries, more and more women today are opting to freeze their eggs early-on and start families once they get settled in their careers. Freezing preserves the same quality and quantity of eggs at the age when they were frozen and hence consider as a hack to pause the ticking clock. The same applies to single males as well. Men who wish to postpone parenthood for medical or social reasons now have the option to freeze their sperm cells. Women with a family predisposition of early menopause due to genetic factors can have reduced fertility potential and a narrow fertility window. This can be identified by measuring the ovarian reserve through blood tests, and as well as through ultrasound scans. Once detected, these women are advised to complete their family at the earliest.

However, if personal reasons preclude this, egg or embryo freezing is an ideal option for them. Preimplantation genetic testing is a genetic test performed on embryos that gives us information about the genetic makeup. This test can identify embryos with the correct number of chromosomes. Transferring healthy embryos will lessen the chances of miscarriage as well as result in healthy babies. Embryos which are free from genetic diseases like thalassemia, sickle cell disease, and other such conditions that run in the family can be identified. Currently, these tests have a turnaround time of a few weeks.

Hence, freezing is a must as an adjunct while the results are awaited. Cancer is not a disease that affects just the elderly. Almost 25-30% of cancer affected men and women have not yet married or had kids. Medical treatments for cancer such as chemotherapy, drugs, and radiation can cure the disease but can also harm fertility. In such situations, choosing to preserve eggs or sperm can give us the chance to have biological children later at an appropriate time. Lastly, there are many couples who are unable to have biological kids and depend on donor eggs or sperm. Altruistic donation and banking of sperm/eggs is the only way to realise the family dream of these couples.

What Is Preserved?

Surplus embryos from the IVF cycle are the most commonly cryopreserved cells. This saves the woman the trouble of undergoing another IVF cycle with all the costs and inconvenience if one cycle fails. Previously, such excess embryos were discarded for some reason, and if the pregnancy was not achieved, the couple were back at square one. With cryopreserved embryos, even if the treatment is a success and pregnancy is also achieved, couple can later come back for their second child to complete the family. Human oocyte or egg is a very delicate cell.

However, with advances in technical expertise, egg freezing has now become a common routine and a safe procedure in experienced hands. Oocyte Cryopreservation is another common term used for egg freezing. Choosing this option keeps open the woman’s chances of having a genetic child beyond the natural fertility period. Eggs are retrieved after stimulating the ovaries with hormones and then preserved. At the chosen time, they may be thawed and injected with sperm to create embryos. These embryos are then transferred to the woman’s or a surrogate’s uterus to produce a biological child. Historically, sperm cells have been the easiest human reproductive tissue to access as well as cryopreserve.

Research in cell freezing have always involved working with sperm cells. Recent discoveries show that sperm cells can tolerate the freezing well and stay alive without compromising their function for more than 20 years. Sperm freezing is also routinely offered to men who work remotely (soldiers, sailors, software professionals working onsite abroad etc.), and to those who can’t be available in person during an IVF cycle.

Apart from these cells, small bits of ovarian tissue can also be frozen. This avoids the IVF process all together and also helps young girls preserve their fertility. Freezing was initially done by a technique called slow freezing, but lately most IVF centres have switched to Vitrification. This new supercooling technique significantly lowers the costs, complexity, and cell damage related to the method. Typically, in any form of freezing, chemicals called solutes are added according to fixed protocols in specific concentrations, which replace water inside the cells and enable freezing. Then they are placed in small vials, labelled and submerged in large cryotanks filled with liquid nitrogen.

Is Cell Freezing Risk-Free?

Cryopreservation is an advanced technique which is reasonably safe and effective. However, having a healthy child involves much more than an egg, sperm, or embryo. How the woman’s body reacts and accepts the implanted embryo depends on her uterus, health conditions, and immunity, which plays a very important role. The loss of frozen embryos is rare but possible despite all precautions. There have been reported instances of loss of precious cryopreserved tissues due to logistic factors such as liquid nitrogen supply and refilling problems, power outages, natural calamities and such. Barring such unforeseen issues, damage during freezing and thawing is more likely due to temperature changes.

Akin to chill burns, freezing of water and ice crystal formation inside the cells kills them. Cells need to be taken to temperatures of -190 degrees carefully for cryostorage. Despite great care, at least 5-10% of stored embryos are damaged or eggs lose their fertilisation potential. Some loss is unavoidable and it is largely overcome by freezing more tissue with a safety margin to allow for loss. Apart from manpower, other expenses including the cost of solutes that needed to freeze cells, cryovials, and liquid nitrogen that needed to be refilled on a regular basis are definitely factors that affect the cost.

Pregnancies achieved from cryopreserved cells account for almost 50% of today’s IVF conceptions. No significant issues have been found so far and there is no harm caused by the freezing technique, chemical solutes used to preserve cells, or the liquid nitrogen used. No viral or bacterial infections affect the tissue when due precautions are taken. IVF babies are under close follow-up in many countries where national registries are maintained. The available information is quite reassuring. Cell freezing has come to occupy a pivotal place in the current fertility practice. It is a unique solution to some problems that cannot be overcome by any other means. It is here to stay, and as science advances numerous other options that yield better results and more convenience at a lower cost are expected to come up.

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