Often after a cycle of IVF or ICSI, there are a number of successfully fertilized embryos that we can freeze and store for your future use.

    Embryo Freezing and Storage

    Often after a cycle of IVF or ICSI, there are a number of successfully fertilized embryos that we can freeze and store for your future use. Whether your cycle was successful or unsuccessful, frozen embryo transfer gives you another chance of pregnancy from the initial egg collection with a much-reduced cost and without having to go through an egg collection again.
    There are two methods of embryo freezing: slow freezing and vitrification. Slow freezing has been used for many years with good results, but vitrification is a newer method showing much higher success rates – often as high as fresh transfers.
    The embryologist will decide if any of your embryos are suitable for freezing. They do need to be of good quality as poor quality embryos do not survive the freezing/warming process.

    Embryos can be frozen at various stages between the cleavage stage (day 2, at about 4 cells) to the blastocyst stage (day 5 or 6). Embryos can be stored frozen for up to ten years.
    To freeze embryos, you must give written consent for Dr. Invitro to store your embryos and for their future use. You must keep in regular contact with Dr. Invitro so that we know if you have moved house or if any of your circumstances have changed. Once the statutory period is up, we do not need your consent to remove the embryos from storage.
    We hope that you are successful from your frozen embryo cycle and hope that you may achieve more than one pregnancy from one full cycle of IVF/ICSI.

    Embryo freezing: What you need to know!

    Embryo freezing is a procedure that allows people to store embryos for later use. A person can also freeze eggs, which are not fertilized. An embryo forms after fertilization and after the cells start to divide.

    The first successful pregnancy resulting from freezing a healthy embryo took place in the 1980s. Since then, many people have frozen embryos and used them later.

    A person may decide to store an embryo if they hope to become pregnant in the future.

    The process begins by using hormones and other medications to stimulate the production of potentially fertile eggs. A doctor then extracts the eggs from the ovaries, either for fertilizing in a lab or for freezing.

    Successful fertilization may lead to at least one healthy embryo. A doctor can then transfer the embryo to the womb, or uterus. If the treatment is successful, the embryo will develop.

    Fertilization often results in more than one embryo, and the doctor can freeze and preserve the remaining embryos.


    What is an embryo, and how do people create one?

    Before freezing can take place, people need to create suitable embryos. To do so in the laboratory, doctors must harvest and fertilize some eggs.

    First, the person will take hormones to make sure that ovulation happens on schedule. They will then take fertility medications to increase the number of eggs that they produce.

    In the hospital, a doctor will extract the eggs, using an ultrasound machine to ensure accuracy.

    A person may wish to freeze their eggs. Or, they may wish to use them at once to become pregnant. In this case, the doctor may recommend in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI).

    During IVF, the doctor exposes the eggs to sperm and leaves them in a laboratory for fertilization to take place. After this, the correct term for a fertilized egg is an embryo.

    An embryologist will monitor the development of the embryos over the next 6 days, after which they may choose a suitable embryo for implantation.

    During ICSI, the doctor extracts the eggs and embryolog injects a single sperm directly into an egg.

    They may do this if there is a problem with the sperm or if past attempts at IVF have not resulted in fertilization. The doctor may use one or two embryos and embryolog may freeze the others. At Dr. Invitro ICSI(Intracytoplasmic sperm Injection)  is used for fertilization. Since ICSI superior to classical IVF in very bad conditions and rate of fertilization better than classical IVF.

    How do people freeze embryos?

    The main aim of freezing embryos is to preserve them for later use.

    The biggest challenge is the water within the cells. When this water freezes, crystals can form and burst the cell.

    To prevent this from happening, the doctor uses a process called cryopreservation. It involves replacing the water in the cell with a substance called a cryoprotectant.

    The embryolog  then leaves the embryos to incubate in increasing levels of cryoprotectant before freezing them.

    After removing most of the water, the doctor cools the embryo to its preservation state. They then use one of two freezing methods:

    Slow freezing: This involves placing the embryos in sealed tubes, then slowly lowering their temperature. It prevents the embryo’s cells from aging and reduces the risk of damage. However, slow freezing is time-consuming, and it requires expensive machinery.


    In this process, the embryolog freezes the cryoprotected embryos so quickly that the water molecules do not have time to form ice crystals. This helps protect the embryos and increases their rate of survival during thawing. At Dr. Invitro’s embryos, eggs and sperms are freezing with vitrification. After thawing procedure embryo, egg and sperm survival rate than slow freezing and almost the same as fresh procedures.

    After the process of freezing is complete, the embryolog stores the embryos in liquid nitrogen.

    How long can embryos stay frozen?

    In theory, a correctly frozen embryo can remain viable for any length of time.

    The embryos remain in sealed containers at temperatures of -192 C. At this temperature, almost no biological processes, such as aging, can occur.

    There are examples of successful pregnancies resulting from eggs that people have stored for up to 10 years. No long-term research into embryo freezing exists because doctors have only been carrying out the procedure since 1983.

    Who can benefit?

    Embryo freezing may be a better option for certain groups, such as:

    • people with genetic disorders that affect reproduction
    • people who will soon undergo chemotherapy
    • people who take medications that affect fertility
    • same-sex couples and other LGBTQ+ people who wish to have children

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