The vitrification of embryos allows the results to be optimised in treatments involving in vitro fertilisation

• This technique has helped to reduce multiple pregnancies and to achieve several pregnancies from a single cycle of ovarian stimulation

• Over the last decade, treatments of IVI patients over the age of 40 have increased by 74%

• With advanced age a higher rate of aneuploidy in embryos generated from damaged oocytes has been recorded, and subsequently an increase in the incidence of miscarriage

ALICANTE, 25 APRIL 2015

Vitrification has become the standard method of cryopreserving oocytes, and when applied to embryos this technique has significantly increased survival rates. As a result, a growing number of reproductive clinics all around the world have adopted vitrification as a customary practice. Thanks to this technique, nowadays it is possible to carry out deferred embryo transfers; in other words, embryos are vitrified after being obtained in an in vitro fertilisation (IVF) cycle in order to be transferred to the maternal uterus at some stage in the future. This strategy can be extremely useful in certain cases in which endometrial receptivity may be affected, or when the transfer of fresh embryos is not recommended for one reason or another.

“The cryopreservation of embryos has been a successful technique since the beginning of the 1980s, although at that time the basic protocol used was slow freezing. Nowadays the process of vitrification, which prevents ice from forming, thus avoiding damage to the embryo, benefits from optimised protocols that have brought great improvements to reproductive treatments, preserving intact the implantation potential of the embryo. As such, we have highly safe and effective cryopreservation programmes at our disposal, which is why we can be confident that what we have stored will produce the desired result,” explained Dr Ana Cobo, Director of the Cryopreservation Unit at IVI Valencia and author of a current study entitled Embryo Vitrification: clinical state of the art.

The implantation rates and clinical results using vitrified embryos are comparable to those achieved with fresh embryos. This is explained by the fact that following vitrification the rate of intact embryos, in other words those that have not suffered any kind of damage, is very high, even reaching 95%.

“Furthermore, vitrification has to a large extent enabled the number of multiple pregnancies to be reduced, as once the embryos have been obtained they can be preserved with the same quality as at the moment when they were harvested, allowing us to opt for single embryo transfer (SET) in an attempt to make assisted reproduction mirror natural conception as closely as possible,” added Dr Cobo.

Using this technique several pregnancies can be achieved from one single ovarian stimulation cycle, which contributes to an increase in the accumulated success rates, making the best possible use of the treatment.

This option is recommended for patients at risk of suffering from ovarian hyperstimulation syndrome (OHSS), deterioration of the endometrium, and for some older women who require Pre-implantation Genetic Diagnosis (PGD) in order to find out whether or not their embryos are genetically and chromosomally normal. In the latter case, it is often necessary to vitrify the embryos while waiting for the results of genetic testing.

In 90% of cases the vitrification of oocytes is indicated for non-medical reasons

Vitrification is a vital technique in reproductive medicine nowadays, in which older women represent a significant portion of the total number of infertile patients. Over the last ten years, treatments of IVI patients over the age of 40 have increased by 74%, and in 2014 alone they accounted for 40% of all treatments carried out by the group in Spain. A growing trend towards later motherhood is requiring assisted reproduction centres to adapt to this social reality.

In 2013 the American Society for Reproductive Medicine recommended ceasing to consider the vitrification and devitrification of oocytes as an experimental procedure. This led to a doubling in the number of clinics offering this technique, 90% of the time for non-medical reasons.

In this respect, this Congress has opened up a discussion concerning the pertinence of vitrifying oocytes from the age of 38 onwards for social reasons.

It is as Dr Linda C. Giudice, from the University of California and author of the study All women beyond 38 years of age should freeze their oocytes, commented: “While the survival of oocytes is similar among women of different ages, including those over the age of 38, success rates decrease as the age of the woman increases at the point when her oocytes are vitrified, just as they do in clinical experience with fresh oocytes”.

As Dr Giudice explained, the main argument for freezing oocytes in women over the age of 38 is that if a fertility treatment is recommended for a patient of that age, vitrification is one of the range of treatments on offer, as what can be done using fresh oocytes can also be done using frozen ones, given that the results in a particular age group do not differ depending on whether the oocytes are fresh or frozen.

Dr Yacoub Khalaf, from Guy’s and St Thomas’ Hospital Foundation Trust in London, stated that the quantity and quality of oocytes decreases considerably beyond the age of 35, added to which there is a progressive increase in the rate of aneuploidy in the oocytes, which goes on to affect the embryos generated from these damaged gametes. “If these embryos implant, the rate of spontaneous abortion rises, and this is due in the main to chromosomal anomalies,” added Dr Khalaf. “Although the desire to preserve fertility by means of freezing oocytes in order to avoid the effect of age on the ovarian reserve is understandable and has been given a substantial boost thanks to the recent improvements in the technique of vitrification, this process seems to be more effective if it is carried out before the age of 35,” he concluded.

Although it is certainly the case that the vitrification of oocytes in patients over the age of 38 is possible, women ought to be aware that the earlier they consider the option of vitrifying their ova, the better their chances will be of achieving their desire to have children in the future.