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Cryopreservation

Embryo Freezing

Embryo Freezing is the technique of freezing embryos in order to safeguard them for future use. The In vitro fertilisation (IVF) method, which employs fertility pills to kindle ovulation, frequently produces scores of embryos after successful execution.However, with advancements in the reproductive medical science, the embryos can now be frozen or cryopreserved for future use by the same couple or by any another couple who wishes to use a donated embryo.

Science behind Embryo Freezing

The tissues of the embryos are sustained by water like any other living organisms. This water content has to be eliminated in order to avoid the formation of ice crystals. These ice crystals may lead to the breakage of the delicate embryo cells. After removing the water content completely, the embryo cells are combined with a cryo-protectant fluid (which avoids formation of ice crystals) and then sealed in a plastic or glass module. With the help of a programmed machine, the complete mixture is frozen in liquid nitrogen at a very low temperature (-196 degrees Fahrenheit).

Thawing of Embryos

The frozen embryos are removed from the container and brought up to the atmospheric temperature during the procedure of thawing. Also, the cry-o-protectant fluid is slowly eradicated and later, it is attenuated with water. The entire process of thawing is done meticulously as the embryo cells are very delicate and break if water is sent into the cells excessively. The embryo is implanted in uterus after bringing it at par with the room temperature.

Who Can Use Frozen Embryos?

The transfer of frozen embryos can be successfully achieved for women with untimely menstrual cycles or by women with other issues related to conceiving. This transfer is stimulated by a natural cycle which involves the priming of the endometrium to enhance its receptivity to the embryos. As the rate of pregnancy with high-quality frozen embryos is as good as that with new embryos, you are thus advised by the experts to freeze and preserve embryos rather than discarding them. Apart from acting as insurance in case of failed fresh embryo transfer, the procedure of freezing an embryo is also considerably less costly than starting a new cycle.

Benefits of Embryo Freezing

Due to the developing technology, it is now possible to freeze these embryos and preserve them in liquid nitrogen. You can make use of your spare embryo at a later stage, if you choose to get pregnant again. The stored embryos enable you to circumvent the repetitive procedure of superovulation and egg collection. In addition, medical experts have the opinion that the receptivity of the uterus to these embryos is better as their transfer is done by natural methods, without involving the usage of any hormonal injections.

Understanding Embryo transfer & Its Steps:

What is embryo transfer?

  • Embryo transfer takes place after eggs have been collected and fertilised in the laboratory.

  • Depending on your situation between one and three of the best quality embryos are selected and then transferred to the woman’s womb.

  • An embryo must successfully attach itself to the wall of the womb for pregnancy to begin.

How does embryo transfer work?

The exact procedure for embryo transfer depends on the clinic you choose. A typical procedure may involve the following:

  • Step 1.

    Two to three days after the eggs are fertilised, the best quality embryos are selected to be transferred to your womb.

    If you are under the age of 40, one or two embryos can be replaced.

    If you are 40 or over, a maximum of three embryos can be used (unless you are using donated eggs, when the maximum is two because these eggs will be from donors who are not older than 35).

    If you have good quality embryos, those that are not transferred can be frozen. Some clinics may also offer blastocyst transfer, where embryos are transferred five to six days after fertilisation.

  • Step 2.

    The doctor or nurse doing the embryo transfer inserts a speculum into your vagina. This is the same procedure as a cervical smear test where the speculum is used to keep your vagina’s wall apart.

    A fine tube (catheter) is passed through the cervix, normally using ultrasound guidance. The embryos are passed down the tube into the womb.

    This is normally a pain-free procedure and usually no sedation is necessary, but you may experience a little discomfort because you need a full bladder if ultrasound is used.

  • Step 3.

    It is generally recommended that you lead a gentle lifestyle during the few days after embryo transfer.

  • Step 4.

    About two weeks after the embryo transfer, you will be given a pregnancy blood test. If it is positive, you will have a scan about two weeks later.


    New technique – Metabolomics


    Researchers are currently developing a new method of embryo selection – Metabolomics. The method could potentially be used to identify embryos with the best chance of implantation.

    Metabolomics involves taking a sample of the fluid (culture media) from the dish an embryo is developing in and testing it for levels of certain molecules (metabolites).

    Researchers are establishing which molecules, and levels of these molecules, corresponds to the most viable embryos.

What are the risks of embryo transfer?

There are no significant risks relating to the embryo transfer process itself.

If you have never had a baby or if the canal of the cervix has not been assessed before the in vitro fertilisation (IVF) cycle was started, there can occasionally be difficulties in passing the embryo transfer catheter through the cervix.

While it is possible to stretch the cervical canal at the time of transfer, your specialist might prefer to avoid such interventions at this time.

In extreme cases, your specialist may decide that it is in your best interests to delay the embryo transfer and freeze all suitable embryos until after the cervix has been stretched.

There are significant risks if more than one embryo is transferred: you may want to consider single embryo transfer.For more information on the problems involved in multiple births, speak to your clinician

What are my chances of getting pregnant after embryo transfer?

Female fertility diminishes with age, so if you are using your own eggs, on average, the younger you are, the higher your chances of success.

In the year 2011 (the year for which the most recent data is available) for women receiving stimulated IVF using fresh embryos created with their own eggs, the percentage of cycles reaching embryo transfer that resulted in a pregnancy (national average) was:

  • 40.6% for women aged under 35

  • 35.5% for women aged between 35-37

  • 28.1% for women aged between 38-39

  • 21.2% for women aged between 40-42

  • 11.2% for women aged between 43-44

  • 3.4% (0/81) for women aged 45 and over