All you need to know about freezing

Freezing sperms, eggs, or embryos at sub-zero temperatures helps a person/couple get ready to have babies later in life. So, if your current focus is financial stability or career growth, pregnancy can be kept on the backburner without having to worry about the quality of eggs and sperm decreasing with age. Freezing embryos can be a good option to have a pregnancy later in life when you are ready.

What is cryopreservation or freezing?

Cryopreservation or freezing simply doesn’t mean cooling of tissue but it is a process where the temperature is gradually lowered so that all the activities of the cell remain intact. Earlier, it was done by a technique called slow freezing which leads to lower survival rates (60-70%). Today, it is replaced by vitrification or rapid cooling with survival rates of 99-100%. The major issue with freezing is the damage produced by the water in the cell getting converted to ice crystals. To minimize this risk, tissues are first protected by a cryoprotectant solution that drains water from the tissue. Tissues are then preserved in liquid Nitrogen in sealed containers at -196o C. Eggs, sperms and embryos can be stored at such temperatures for an indefinite period, but storage incurs a cost, so the storage time period depends on the needs of the person who is storing them. When the person/couple decides to conceive, the frozen sperms/eggs/embryos are rehydrated by ensuring that the embryo doesn’t blow up. This process is called thawing. The survival may not be 100 % as a number of cells may get destroyed during the freeze-thaw process.

Cryopreservation is used in two situations:

1. Fertility preservation: either due to disease [ malignancy, autoimmune ] which is likely to impair the reproductive potential or due to social reasons [ career or otherwise ]

2. As a part of the IVF process where extra embryos are stored for future usage.

Eggs and Embryos – what is the difference?

Egg freezing is used when the woman is not married or does not have a stable partner. The process is the same – removing the eggs followed by vitrification and storage in liquid nitrogen. The difference, however, is in how it can be used when needed. The egg has to be thawed or warmed [ brought out from -196 C to room temperature ], checked for survival, and fertilized with sperms to generate embryos that are then transferred into the uterus. All eggs may not survive [ survival is generally 90 – 95 % ], all eggs may not fertilize and generate embryos [ this is generally 50 – 60 % ]. Whereas in the case of embryo freezing, embryos are created before they are frozen and when needed simply thawed [ > 95 % survive ] and used. So, we need a much higher number of eggs to achieve the same results that are obtained by embryo freezing. This number depends on the age of the woman and egg quality.

Why freeze embryos?

It is a known fact that the quality of a woman’s egg and a man’s sperm decreases with age especially after the age of 35. In fact, age is one of the most common infertility risk factors. Because of this, many couples prefer to create embryos when they are young and freeze them so that they can have babies later. Experts suggest those mulling about freezing embryos should do the procedure at 32-33 years of age when the eggs and sperm are relatively healthy.

In all IVF procedures, drugs are given to stimulate the ovaries to produce more eggs. Hence, many times there will be a higher number of embryos. All such surplus embryos can be frozen and used later – for a second child when the first attempt is successful or for a second attempt if the first one fails.

Freezing or cryopreservation may be opted by men, women or couples for fertility preservation:

In unmarried men and women, this is primarily used when they suffer from malignancies or certain autoimmune disorders where they are expected to receive chemotherapy or radiation which is likely to destroy their reproductive function. It is also used by women who suffer from progressive disorders like endometriosis or chocolate cyst which gradually destroys ovaries. In men, testicular tissue or sperms may be frozen whereas in women eggs or ovarian tissue may be frozen. In couples, it is advisable that embryos are created and frozen. Social freezing is performed when a person/couple is not ready to have a child and want to delay it for career or other reasons. Freezing gametes/embryos at a young age give them a better chance when they want to have a pregnancy at an older age.

Cryopreservation as a part of the IVF program:

In IVF programs, injectable drugs are given to form multiple eggs and this often leads to the formation of supernumerary embryos. Sometimes, the condition of the uterus is also not favorable for embryo transfer and it is advisable to freeze the embryos and transfer them subsequently. If the woman conceives after the embryo transfer, the remaining frozen embryos can be used later for planning the next pregnancy. Similarly, if the result is negative after the embryo transfer, the women can plan the next attempt with these frozen embryos.

How is a frozen embryo transferred?

This is a simpler process and involves the thawing of a previously cryopreserved embryo and transferring it in the uterus after optimal endometrial preparation.

  • A frozen embryo transfer is a much simpler process and does not require any injectables or anesthesia for egg extraction. It involves intake of oral and vaginal tables to prepare the uterus for the pregnancy
  • The cost of frozen embryo transfer is significantly less compared to a fresh IVF cycle
  • The success rate of embryo transfer using frozen and subsequently warmed embryos is equivalent to a fresh transfer
  • Frozen embryo transfer freezes the age: It gives the same success rate as that of the biological age at which the embryos were frozen. For e.g. if a woman undergoes an IVF cycle at 28 years and conceives and freeze the extra embryos, even if she plans another child at 35 years, she will get the same success rate with the frozen embryo transfer as before (equivalent to what she had at 28 years)

To what extent do embryos survive freezing?

It depends on the process and technology used to freeze embryos. Traditionally a slow freezing cryopreservation method was used; vitrification is a relatively newer and emerging technology.
In early studies, it was suggested that embryos survive freezing better than eggs when the slow freezing technique was involved. This is because an egg is made up of a single cell, unlike an embryo that is made up of multiple cells. This makes an embryo stronger to survive freezing better.

But with technology like flash freezing (called vitrification), it has been shown that eggs and embryos can survive thawing to almost the same extent. As per studies, 95% of embryos (as compared to 90% of eggs) survive the freeze-thaw process.

To What if the embryos remain unused after being frozen?

Embryos frozen for a couple can either be used by the Couple or they have to be discarded or donated to a recognized research body for medical research. They can not be donated to another person/couple. If one of the partners dies or the couple gets divorced, the embryos are given to one of the partners based on the consent given at the time of freezing.

Freezing embryos is an excellent way to maintain the quality of embryos while delaying a pregnancy. If you have decided to take this step, make sure you choose a qualified fertility hospital to carry out this procedure. At Dr. Banker’s, we offer advanced fertility treatment options, donor treatments, and fertility counselling to ensure that every step of your journey to parenthood is taken care of.

If you’re looking for IVF treatment in Vadodara, Rajkot or IVF clinics in Meshna, you can easily visit Dr. Banker’s in Ahmedabad and freeze your embryos as well as receive IVF treatment.

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