A new life from deep freeze to parents’ loving arms – Pregnancies via frozen embryo transfers (FET) and egg freezing

27.8.2016 Pekka Sillanaukee

A new life from deep freeze to parents’ loving arms – Pregnancies via frozen embryo transfers (FET) and egg freezing

With modern fertility treatments life begins with deep-freezing, as embryos can now be safely frozen and stored for future use. This means that the same family can have children who were conceived on the same day but born in different years. Technological progress has also made it possible to freeze and store eggs. This gives us the chance to retain the fertility of women who want to postpone having children because of their situation in life. The frozen embryo transfers (FET) performed at Ovumia clinics have resulted in more than 42,000 frozen embryos and 7,500 births. Sometimes it takes some time for a human embryo to get from deep freezing to his or her parents’ warm and loving arms.

There was recently discussion in the media about the coldest place on earth with permanent inhabitants. It turns out to be the village of Oymyakon in Russia where the average winter temperature is -50 °C and where the coldest temperature measured was -71 °C in 1926. Interestingly, numerous embryos conceived in vitro spend the first months or years of their lives in a much colder environment, i.e. deep frozen at -196 °C.

With in vitro fertilisation treatments, an average of 7-15 eggs are collected which, after fertilisation, develop into several embryos. The best embryo is transferred into the uterus to continue its growth there, leaving many other embryos of good quality to be used later. In modern fertility clinics, such as Ovumia, 70 % of treatments involve transferring only one embryo with excellent pregnancy results. This makes a normal pregnancy possible and ensures a safe childbirth for both the mother and child.

Thanks to the developments in embryo freezing methods, the remaining embryos can be frozen and stored for future use. Sometimes, though rarely, an embryo is not transferred immediately in connection with the in vitro fertilisation treatment and all the embryos are frozen instead. Deep-freezing embryos also means that if the first treatment cycle does not produce a positive result, the woman does not need to undergo a new cycle of hormone treatment for ovarian stimulation, but the transfer of the frozen embryo can be carried out either during the woman’s natural menstrual cycle or utilising compensatory hormone treatment. When the mucous membrane of the uterus is at the optimal stage, one or more of the frozen embryos are thawed and then transferred into the uterus (frozen embryo transfer or FET). Embryos can be stored in deep freeze for long times and they can be thawed when you want a second or third child. This means that the same family can have children who were conceived on the same day but born in different years. Embryos are not affected by the time they are frozen. Instead, what is crucial for the embryo is its quality at the time it was frozen and the methods used for freezing and thawing it.

The first ever child conceived via FET treatments was born in 1984 in Australia. Today, embryo freezing is a common procedure at fertility clinics. Frozen embryos are stored in liquid nitrogen at -196 °C in monitored laboratory conditions. Embryo freezing is an important part of in vitro fertilisation, because it has allowed for safer and more effective treatments.

In 2014, there were 2,417 babies born as a result of all the fertility treatments performed in Finland and 730 of these resulted from treatments involving FET. This is more than the number of babies born as a result of in vitro fertilisation (IVF, 531), intra-cytoplasmic sperm injection (ICSI, 397) or intrauterine insemination (IUI, 466). (National Institute for Health and Welfare, 2016.)

To prevent the formation of ice crystals which may cause damage later, we use special solutions in embryo freezing, which contain protective compounds. The two methods mainly used today for embryo freezing are slow-rate freezing and vitrification. The former involves freezing embryos slowly over a period of about two hours from room temperature to -196 °C. The latter, vitrification, is a quick freezing method that has become more common in recent years. It only takes a few minutes and involves using a greater concentration of protective agents to prevent the formation of ice crystals. The embryos to be frozen are put in special frost-resistant tubes which are labelled with the customer’s name and individual code. The tubes are then placed in tanks containing nitrogen until they are thawed for use.

Some individual embryos do not survive freezing and thawing. With the traditional slow-rate freezing method, the embryo preservation rate after thawing is about 50–70%. Also, the embryos of some individual customers may all survive, while the preservation rate for others may be lower. Thanks to the development work Ovumia has engaged in to improve the vitrification method, the embryo survival rate after thawing is 90%, allowing us to reach better pregnancy results. Another advantage of vitrification is the fact that it is suitable for all stages of embryo development – even the delicate eggs – whereas slow-rate freezing is best suited for embryos in the cell division stage.

In the Ovumia fertility treatment laboratory, embryos are usually thawed a day before the embryo transfer. The next morning, we check their development. If they have not developed as expected, the transfer is not performed. FET treatment results by vitrification are usually excellent. For example, the FET treatments performed at Ovumia resulted in 40% clinical pregnancies, while the national rate of clinical pregnancies using FET was 27% in 2014.

Over the last few years, freezing eggs has also become possible and it is offered to women more and more. For women with a partner we recommend egg fertilisation and freezing the embryos. Storing eggs is more difficult than storing embryos because eggs contain a large quantity of cytoplasm. With the egg freezing method developed at Ovumia, eggs can be stored for both medical and social reasons. Proactive freezing refers to salvaging a woman’s eggs at a younger age to preserve her fertility. This gives us the chance to retain the fertility, for example, of women who do not have a regular partner or who want to postpone having children because of their situation in life. We recommend egg freezing before the age of 35. Freezing eggs at a younger age increases a woman’s likelihood of having children when they are older.

Today, the first babies born through the FET method are 30 years old and many of them are parents themselves. Recent studies have shown that FET treatments result in fewer premature births in single-foetus pregnancies than embryo transfers performed without freezing. In short, the importance of FET lies in the fact that when one cycle of treatment and fertilisation results in several embryos, freezing them allows us to perform embryo transfers more times, which increases the probability of pregnancy.

Children born via freezing treatments are just as healthy or more healthy than those born via other fertility treatments. These days, many experts have actually suggested that all fertility treatments could be performed using frozen embryos, because a woman’s body is then better prepared than with in vitro fertilisation treatments involving ovarian stimulation with hormones.
More than 42,000 embryos have been frozen at Ovumia clinics and 27,000 of them have been transferred. Our treatments have brought about more than 7,500 children. This is all a clear indication of Ovumia’s extensive experience and expertise. And, of course, the best part of our work is being visited every year by many happy families who come to show us their own little miracles, their children. It is a long journey from storage to the warm and loving arms of adoring parents.

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