Embryo Freezing (Cryopreservation)



When a sperm enters an egg, the egg is said to be fertilized, and is called an embryo. The resulting embryo may be viewed as potential human life, or in the view of some, a human life. Following human in vitro fertilization, embryos may be produced in the laboratory which cannot be immediately replaced into the uterus. This occurs principally as a result of multiple eggs being fertilized, and the current practice of replacing no more than a specified limited number of embryos in the uterus at one time. At other times, an egg may be immature, and its fertilization delayed to the point where the uterus is no longer receptive to implantation. In both cases it is our practice to offer the patient an opportunity to cryopreserve (freeze) normally developing embryos for future use. However, embryo freezing is not a necessary part of the in vitro fertilization process. It is an elective decision that each couple must decide about prior to the actual follicular aspiration.

Embryos are frozen in the in vitro fertilization laboratory in special holding containers (freezing straws) in which they are suspended in a small volume of supporting medium and a special freezing solution (cryoprotectant). During the freezing process, the embryos are brought to a temperature of -196º C. They are then submerged in liquid nitrogen in storage tanks. The embryos can be kept in liquid nitrogen indefinitely. Embryos may be frozen at any stage of development, from one cell to blastocyst (100 cell), or from one to five days after fertilization. In order for frozen embryos to produce a pregnancy, they must be thawed and then replaced in the uterus at the correct time of the menstrual cycle. Therefore, the day of embryo replacement varies with the stage at which the embryos are frozen. The transfer of previously frozen embryos is electively scheduled and you will be instructed as to the exact day of the cycle when the embryos will be replaced. It is not uncommon for a patient to have groups of frozen embryos cryopreserved at different stages and requiring different cycles of frozen embryo transfer.

When embryos are frozen, their likelihood of producing a pregnancy is reduced. However, patients who fail to achieve pregnancy with fresh embryos may become pregnant during subsequent embryo transfers using their frozen embryos. A small proportion (about 20%) suffer sufficient damage during freezing that at the time of thawing, they are no longer viable. Rarely, all of a couple’s frozen embryos are found to be non-viable and the transfer is cancelled. In order to have a reasonable chance of producing a pregnancy after thawing, the embryo must demonstrate normal development and appearance (“morphology”).

Risks and Benefits of Embryo Freezing


The benefit of embryo cryopreservation is the is the preservation of embryos for use during a future IVF cycle, thereby lowering the risks of multiple pregnancies by limiting the number of embryos transferred in an initial cycle, and increasing the chances of a pregnancy by transferring during a cycle without the additional risks and expenses of egg retrieval. We understand that completing this consent for cryopreservation does not guarantee that there will be any excess embryos available for cryopreservation.

The risks of cryopreservation are that the frozen embryos may not survive the freezing or thawing process or that a pregnancy will not occur. We also acknowledge that the freezing of embryos requires the use of mechanical support systems and the involvement of human technicians. We recognize that the practice of medicine is not an exact science and understand that techniques for embryo cryopreservation and thawing are relatively new, and are not universally established. We acknowledge that human error, equipment failure or unknown factors could negatively affect the viability of the embryos. We specifically acknowledge and agree that RFC or any of its employees will not be liable for any destruction, damage, or loss to our embryos as a result of freezing, maintenance, storage, removal from storage, thawing, and/or delivery of the frozen embryos, or related services. We also acknowledge that any non-viable embryos, as determined by the embryology laboratory, may be discarded.

There may be a risk of infants having developmental defects as a result of frozen embryos being thawed; however, initial human experience and extensive experience in domestic animal species have not yet demonstrated and increase in deformed offspring beyond that observed in natural conception.

Media utilized for IVF and associated procedures (Assisted Hatching, Intracytoplasmic Sperm Injection, Embryo Transfer, etc.) may contain commercially obtained serum or serum components. While every effort to screen these products for hazards (e.g. HIV, hepatitis, etc.) has been made, the potential for unforeseen hazards is present and hereby acknowledged.

Some nonphysical risks of participation may include increased time commitments and travel considerations, financial implications, risks related to insurability and employment, and psychological effects.

Treatment Alternatives


Alternatives to freezing embryos are:

  1. Implanting all fertilized eggs into the Female Partner’s uterus, subject to the physician’s medical opinion as to maximum number;
  2. Discarding the excess embryos not transferred in the initial cycle.
  3. Allowing excess embryos to be adopted by other infertile couples.


Costs and Expenses


The costs associated with egg freezing, cryopreservation, storage and thawing are separate from those associated with in vitro fertilization treatment, and insurance coverage may not be available to cover those costs. Before you begin an in vitro fertilization cycle, all potential fees for embryo freezing and storage will be discussed with you.

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