BIOMATERNITY Fertility and IVF Specialsts-VITRIFICATION 1

Cryopreservation

“Cryopreservation involves the slow freezing of cells in order to maintain the existing form, structure and chemical composition of all of their constituent elements for future use.”

Vitrification

“Vitrification involves the transformation of a liquid to a glassy solid i.e., without the formation of crystals during the cooling process.”

Freezing of sperm greatly improves the flexibility of assisted reproduction treatments in cases when:

  • donated sperm is required, or
  • when it not feasible to obtain a sample on the day of the treatment.

Even though cryopreservation (slow freezing) for sperm cells is an efficient method for preserving sperm for future use without altering its constituent elements and thus its efficacy for fertilization, it is not an effective method for preserving eggs or embryos due to their form and physiology which allows the production of ice crystals, which has a deleterious effect on them and compromises their survival rate.

Vitrification is an innovative advanced method of ultrarapid freezing which prevents the formation of ice crystals and ensures an undamaged post thaw structure. With the advent of vitrification method, freezing and storage of eggs and embryos has become effective and without a loss of viability. Pregnancy rates with the use of either frozen eggs or frozen embryos are now almost equal to those using fresh eggs or embryos.

Vitrification of eggs and embryos is indicated when:

  • a surplus of eggs is produced during assisted reproduction treatments for an eventual subsequent use, or
  • whenever it is medically recommended as in cases where there is an unsuccessful response to medication used to induce ovulation or for a better preparation of the endometrial receptivity.

 Sperm Freezing and Storage

Sperm can be frozen for future use either in artificial insemination or other fertility treatments, or be donated.

Donated sperm has to be stored for six months before it can be used in treatment, in order to screen the donor for infections.

Sperm cells have been frozen, thawed and successfully used in treatment for more than 40 years, although not all sperm survive the freezing process.

Is sperm freezing and storage for me?

Storing your sperm may enable you to use them for treatment in the future. You may want to consider freezing your sperm if:

  • you have a condition, or are facing medical treatment for a condition (e.g. cancer), that may affect your fertility,
  • you are about to have a vasectomy,
  • you have a low sperm count or the quality of your sperm is deteriorating,
  • you have difficulty producing a sample on the day of fertility treatment
  • you are at risk of injury or death,
  • you are about to undergo a sex change operation.

 

What happens when sperm are frozen?

Before you agree to the freezing and storage of your sperm, your clinician will explain the process involved.

You will be screened for infectious diseases, including HIV and hepatitis B and C.

You will need to give written consent for your sperm to be stored.

At the clinic, you produce a fresh sample of sperm.

All sperm is frozen and then stored in a storage tank containing liquid nitrogen.

How much control do I have over what happens to my sperm?

When you first freeze your sperm, the clinic will ask you to fill out consent forms.

The forms allow you to specify:

  • what will happen to your sperm should you become unable to make decisions for yourself or die how long you want to store your sperm (the standard storage period is 10 years),
  • whether your partner (if you have one) can use the sperm later to create a family and whether you wish to be recorded as the father of any child born as a result of fertility treatment after your death,
  • whether your sperm can be used in research or donated for use in someone else’s treatment,
  • any other conditions you may have for the use of your sperm.

You can vary or withdraw your consent at any time, either before treatment or before the sperm are used in research.

BIOMATERNITY Fertility and IVF Specialsts-VITRIFICATION 2
BIOMATERNITY Fertility and IVF Specialsts-VITRIFICATION 1

Cryopreservation

“Cryopreservation involves the slow freezing of cells in order to maintain the existing form, structure and chemical composition of all of their constituent elements for future use.”

Vitrification

“Vitrification involves the transformation of a liquid to a glassy solid i.e., without the formation of crystals during the cooling process.”

Freezing of sperm greatly improves the flexibility of assisted reproduction treatments in cases when:

  • donated sperm is required, or
  • when it not feasible to obtain a sample on the day of the treatment.

Even though cryopreservation (slow freezing) for sperm cells is an efficient method for preserving sperm for future use without altering its constituent elements and thus its efficacy for fertilization, it is not an effective method for preserving eggs or embryos due to their form and physiology which allows the production of ice crystals, which has a deleterious effect on them and compromises their survival rate.

Vitrification is an innovative advanced method of ultrarapid freezing which prevents the formation of ice crystals and ensures an undamaged post thaw structure. With the advent of vitrification method, freezing and storage of eggs and embryos has become effective and without a loss of viability. Pregnancy rates with the use of either frozen eggs or frozen embryos are now almost equal to those using fresh eggs or embryos.

Vitrification of eggs and embryos is indicated when:

  • a surplus of eggs is produced during assisted reproduction treatments for an eventual subsequent use, or
  • whenever it is medically recommended as in cases where there is an unsuccessful response to medication used to induce ovulation or for a better preparation of the endometrial receptivity.
BIOMATERNITY Fertility and IVF Specialsts-VITRIFICATION 2

 Sperm Freezing and Storage

Sperm can be frozen for future use either in artificial insemination or other fertility treatments, or be donated.

Donated sperm has to be stored for six months before it can be used in treatment, in order to screen the donor for infections.

Sperm cells have been frozen, thawed and successfully used in treatment for more than 40 years, although not all sperm survive the freezing process.

Is sperm freezing and storage for me?

Storing your sperm may enable you to use them for treatment in the future. You may want to consider freezing your sperm if:

  • you have a condition, or are facing medical treatment for a condition (, that may affect your fertility,
  • you are about to have a vasectomy,
  • you have a low sperm count or the quality of your sperm is deteriorating,
  • you have difficulty producing a sample on the day of fertility treatment
  • you are at risk of injury or death,
  • you are about to undergo a sex change operation.

 

What happens when sperm are frozen?

Before you agree to the freezing and storage of your sperm, your clinician will explain the process involved.

You will be screened for infectious diseases, including HIV and hepatitis B and C.

You will need to give written consent for your sperm to be stored.

At the clinic, you produce a fresh sample of sperm.

All sperm is frozen and then stored in a storage tank containing liquid nitrogen.

How much control do I have over what happens to my sperm?

When you first freeze your sperm, the clinic will ask you to fill out consent forms.

The forms allow you to specify:

  • what will happen to your sperm should you become unable to make decisions for yourself or die how long you want to store your sperm (the standard storage period is 10 years),
  • whether your partner (if you have one) can use the sperm later to create a family and whether you wish to be recorded as the father of any child born as a result of fertility treatment after your death,
  • whether your sperm can be used in research or donated for use in someone else’s treatment,
  • any other conditions you may have for the use of your sperm.

You can vary or withdraw your consent at any time, either before treatment or before the sperm are used in research.

Egg and Embryo Vitrification

During In Vitro Fertilization treatment (IVF), a surplus of oocytes is produced which results in a surplus of embryos which must be preserved. Due to the recent tendency in ART treatment to transfer fewer embryos in order to avoid multiple pregnancies, partly a result of new laws and guidelines aimed at controlling the number of embryos to be transferred and the number of oocytes to be fertilized, the need for simpler, more effective methods for the cryopreservation of embryos and oocytes is increasing. Currently, zygotes and embryos are typically cryopreserved by means of the traditional slow-rate freezing protocol.

However, during the slow freezing method, ice crystals are formed or produced, which has a deleterious effect on the cells. Intracellular ice crystals can damage the cell wall and structure, while the extracellular precipitation of water as ice crystals increases the salt concentration to levels that cause damage to the cell. A delicate balance between these potentially harmful factors must be maintained throughout the slow freezing process to ensure survival of the cells.

Vitrification is an advanced cell-freezing technique, which allows a higher survival rate after thawing due to the fact that high concentrations of cryoprotectors are used along with reduced volumes and timings. Thus, the formation of intracellular ice crystals is prevented, which are responsible, in most cases, for provoking irreparable cell damage.

The vitrification process is used to freeze oocytes or embryos and it guarantees a survival rate of more than 80%. This technique enables the vitrified oocytes which have survived the thawing process to have similar attributes to fresh ones. They are then able to be fertilized by the spermatozoa. The generated embryos can then be implanted and developed into healthy children. Although the implantation rate is lower than with fresh embryos, frozen embryos, once thawed, achieve a normal pregnancy.

Although sperm and embryos have proved easy to freeze, the egg is the largest cell in the human body and contains a large amount of water. When frozen, ice crystals form that can destroy the cell. Over the years, we have learned that we must dehydrate the egg and replace the water with an “anti-freeze” cryoprotectors prior to freezing in order to prevent ice crystal formation. We also learned that because the shell of the egg hardens when frozen, sperm must be injected with a needle to fertilize the egg using a standard technique known as ICSI (IntraCytoplasmic Sperm Injection).

Eggs are frozen using either a slow-freeze method or a flash-freezing process known as vitrification. Currently, we use vitrification for all egg freezing.

Egg freezing can be beneficial for a number of reasons for women wishing to preserve their fertility for the future including:

  • Women who want or need to delay childbearing in order to pursue educational, career or other personal goals (see Egg Social Freezing).
    Because fertility is known to decline with age, freezing your eggs at an early reproductive age will best ensure your chance for a future pregnancy. Unlike the ovary and oocytes (eggs), the uterus does not age and can carry a pregnancy well in to the 40s and 50s. Frozen (cryopreserved) eggs are stored at -196 degrees, so there is no deterioration in egg quality with time.
  • Women diagnosed with cancer.
    Egg freezing offers a chance to preserve eggs prior to chemotherapy, surgery or radiation. Most of these treatments destroy the eggs and lead to infertility. In some cases, viable eggs may be present after cancer treatment. Fertility preserving options vary depending on age, type of cancer, and cancer-treatment plan (see Fertility Preservation).
  • Women with a family history of early menopause.
    Some forms of early menopause (premature ovarian failure) are genetically linked. Egg freezing offers a chance to preserve eggs before they are all depleted (see Fertility Preservation).
  • Women with objections to storing frozen embryos for religious and/or moral reasons.
    Following a standard IVF process, many individuals or couples have excess embryos. The decision to freeze these unused embryos may be difficult because the options for embryo disposition – how, when or if they will ever be used – can be an ethically and religiously complex choice for many. The decision to fertilize only as many eggs as will be utilized in the IVF process and freezing the remaining un-fertilized eggs may offer a positive solution for those with concerns about freezing embryos.

Other reasons may include:

  • supernumerary oocytes,
  • risk of hyperstimulation,
  • no available sperm,
  • repeated previous implantation failures with good quality embryos and
  • patient request for personal reasons.

Following fresh embryo transfer in a stimulated IVF cycle, supernumerary embryos are available for cryopreservation in a large number of cycles. In a routine IVF practice, more than half of stimulated IVF cycles may yield surplus embryos suitable for cryopreservation.

In addition to enhancing the clinical benefits and cumulative conception rate possible for a couple following a single cycle of ovarian stimulation and IVF, a successful cryopreservation programme offers other benefits including the possibility of avoiding fresh embryo transfer in stimulated cycles with a potential for ovarian hyperstimulation syndrome, or in which factors that may jeopardize implantation are apparent (e.g., bleeding, unfavourable endometrium, polyps or an extremely di cult embryo transfer).

The first reports of successful human blastocyst cryopreservation were published in 1985 but blastocyst freezing became routine in IVF only after media for effective extended culture became available during the 1990s.

Extended culture to blastocyst stage is now routine in many IVF laboratories, and the companies that supply blastocyst media also offer blastocyst cryopreservation media and protocols. Glycerol is the cryoprotectant of choice for slow freezing of blastocysts, and extra sucrose dilutions in the thaw have led to a substantial overall improvement.

Using strict criteria to select potentially viable blastocysts is crucial to success:

  • Growth rate: expanded blastocyst stage on Day 5/ Day 6.
  • Overall cell number >60 cells (depending on day of development).
  • Relative cell allocation to trophectoderm/inner cell mass.
  • Original quality of early stage embryo: pronucleus formation and orientation, blastomere regularity, mono-nucleation, fragmentation, appropriate cleavage stage for time of development.

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