Egg freezing and embryo freezing: what’s the difference and when should you choose them?

The supermodel Bianca Balti she said that she had decided to freeze some oocytes so as not to limit her possibility of becoming a mother again. Also Jennifer Aniston she recently spoke about her experience with IVF and regretting not having frozen her own eggs at the time. Egg freezing has existed for several years, but only recently, in Italy, has it begun to be talked about more frequently. A technique is also suggested to cancer patients: chemotherapy and radiotherapy are toxic to the ovaries, and if the oocytes are not preserved, the tumor will be cured but in all likelihood one will remain sterile.

Another option for those who want to preserve their fertility is embryo freezing, a treatment that has existed for much longer than egg freezing, but which has different implications and regulations, especially in Italy. So what are the main differences between embryo freezing and egg freezing? And how to decide which of the two techniques is right for you?

We asked the gynecologist Daniel Gallianodirector of the Clinic specialized in Reproductive Medicine IVI From Romeand author of the book How much I wish you – How medical science helps you to have a child (Edizioni Piemme), to clarify our ideas in this regard.

Dr. Galliano, what exactly is meant by egg freezing and for embryo freezing?
«They are both medically assisted procreation techniques. L’egg freezing consists
in freezing the oocytes at a temperature of -196° and preserving the woman’s fertility
to be more likely to get pregnant later on
freezing, in the event that this fails to occur spontaneously.
L’embryo freezing it is one of the most used techniques in a fertilization process
assisted, as allows you to store unused embryos – for example in
IVF cycles or egg donation – in liquid nitrogen at -196° and be able to
use in case of failure of the first attempt or, for those who have already obtained a first one
pregnancy, if you intend to want another one or if it is advisable for clinical reasons
resort to a deferred transfer.

When do you resort to one case and when to the other?
“Both techniques have the same goal: to keep the biological material in
so that you can get pregnant after freezing, e
they therefore represent the progress made by science in this field. L’egg freezing
it is a procedure that allows you to give women an important aspect in their own
lives: time, why carry out this technique when the woman’s fertility is
greater, therefore before the age of 35, allows higher success rates and then
greater serenity when you want to use them to get pregnant,
after medical evaluation of the possible risks of infertility. Embryo freezing is one
procedure used when one is already within a PMA pathand then
with respect to the fertility problem and the recommended procedure for the couple, in which the
Embryos that are not transferred into the woman’s uterus are kept for
future”.

Are there “technical” differences?
“The freezing process is common to both procedures. Under the PMA,
the Istituto Superiore di Sanità distinguishes between “slow” and “rapid” freezingthe difference
lies in the technique and protocol used. In the case of egg freezing we proceed to freeze
the oocyte, i.e. the female reproductive cell, while in embryo-freezing the freezing of the embryo, i.e. the first stage of development of the fetus, takes place. In the slow freezing, after being collected, the gametes or embryos are exposed to freezing solutions according to a defined protocol to then be loaded into a machine (Planner) capable of reaching the temperature in a controlled manner and according to a pre-established cooling curve of -150 degrees to then be directly immersed in liquid nitrogen (-196ºC). The thawing procedure takes place through several steps in order to avoid damaging the cells. The most concrete risk of this technique consists in the potential formation of ice crystals which could compromise the integrity of the membranes and therefore the vitality of the cells themselves. Over time, a technique has been developed rapid freezing defined vitrification, the main advantage of which consists in the absence of ice crystal formation: the embryos or gametes, in fact, after a process of ovarian stimulation are removed, protected with cryoprotective substances and immersed directly in liquid nitrogen at -196 degrees. The concomitant presence of cryoprotectants and the rapid reduction in temperature causes the liquid state to pass into the solid state in the absence of ice crystal formation in the process. A meta-analysis published in 2017 in the journal Human Reproduction Updateconfirms vitrification as the most effective methodology, in fact in the IVI laboratories it has been the procedure chosen for 10 years now».

What advantages do they offer to women and couples?
«The possibility of cryopreserving embryos and oocytes has opened up new encouraging prospects for people who wish to become parents, using these methods with the aim of maintaining and safeguarding their fertility. We know that the passage of time leads to a progressive reduction in fertility, in fact after the age of 35 in women there is a reduction in the number of ovules both in terms of quantity and qualityand represents a physiological condition that often contrasts with life choices that can determine the shift of future motherhood, determined by personal, social, work and, last but not least, health reasons. Egg freezing therefore represents a sort of therapy for possible cases of future infertility. For couples, after the Constitutional Court eliminated the limit of three storable embryos in force until 2009 by law 40/2004the chances of success in an MAP process have been optimised, given that in this way the woman will have to undergo a single cycle of ovarian stimulation – from which she will then try to fertilize a greater number of oocytes – and in parallel reduce the rate of twin pregnancies by no longer having to transfer multiple embryos at the same time”.

What is it possible to do in Italy currently and what is not possible?
«In our country, the aforementioned Law 40/2004 regulates access to these techniques and establishes that to treat fertility problems, it is possible to resort to assisted fertilization in cases where there are no other effective therapeutic methods to remove the causes of sterility or infertilityadding that couples of adults of different sexes, married or cohabiting, of potentially childbearing age and both living can access it. The Constitutional Court subsequently intervened on the matter, eliminating the maximum limit for the production of three embryos and the obligation to implant them at the same time, considering it incompatible with the principles of protection of women’s health. There are still many limitations to PMAfor example access to heterologous fertilization by homosexual couples or single women is not permitted. Just as, unlike countries such as the UK, Canada, Denmark, Belgium and Australia, there is a ban on surrogacyi.e. the implantation of the embryo obtained by a couple in the uterus of another woman».

Pregnant, after a tumor, thanks to frozen eggs 14 years ago. In Bologna, the first case in the world

Lydia and Timothy, the twins born from cryopreserved embryos 30 years ago

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