When should you freeze your eggs? What is the cost? Watch the recording of the live webinar with Prof. Luciano Nardo, MD MRCOG, Consultant Gynaecologist & Specialist in Reproductive Medicine, to find out more about egg freezing.
In the last 25 years, scientists and clinicians have worked together to optimize methods and clinical protocols for egg freezing. The first human birth from cryopreserved oocytes was reported in 1986. Various studies have looked at the outcomes of fresh versus frozen oocytes, with comparable results.
ASRM (American Society for Reproductive Medicine) found ‘elective egg freezing to be ethically permissible, as enhancing reproductive autonomy and promoting social equality’. However, it should not be used as a form of reproductive insurance. The reason it cannot be considered as a form of reproductive insurance is that there is no guarantee, irrespective of the total number of cryopreserved eggs, that those eggs will fertilize successfully and more importantly will lead to a successful pregnancy outcome. The benefits of egg freezing include the storage of tissue to treat possible future health issues, individuals freezing eggs are healthy individuals at the time of the intervention, it is an established procedure. To some extent, it helps to avoid or reduce the need for egg donation at a later stage.
There are various indications for undergoing egg freezing, medical indications, for example, in cancer patients, the use of egg freezing for egg donation purposes and social reasons. One of the most common reasons for egg freezing is delaying pregnancy. Women choose to delay pregnancy for various reasons, including demographic forces, workplace factors, lack of a partner, and raising costs of childbearing.
One of the papers published in the American Journal of Fertility and Sterility showed that the reasons for deciding egg cryopreservation in 88% of cases were down to the lack of a partner, which means a lack of a stable relationship. It is established that oocyte freezing technology may bridge the gap between reproductive prime and when a woman is ready to have children. According to the paper, the likelihood of women using their cryopreserved eggs is only 6%, while 34% said it’s very likely that they will be using their cryopreserved eggs, and 60% commented that it is somewhat likely.
Egg freezing – limits & risks
Women that cryopreserve eggs after 35 are likely to have poor-quality eggs, and they should be very well-prepared and counselled about the limitations of egg freezing. Therefore, chronological age itself is not the only determining factor when it comes to fertility potential. Other things include:
- woman’s ovarian reserve
- Ovarian Hyperstimulation Syndrome (OHSS)
- the surgical procedure to harvest eggs
- sedation/ anaesthesia
However, on a positive note, there is evidence coming from the publication that said that the use of egg freezing does not increase adverse pregnancy problems or maternal or fetal problems.
It’s important to keep in mind that there is a close relationship between the age when the eggs are cryopreserved and the probability of live birth.
Chronological age is very essential, and how ovarian reserve is assessed is an essential factor. There are two main tests to check your ovarian reserve. The first one is AMH (Anti-Müllerian hormone), which is done by blood, or by doing an ultrasound scan at the beginning of the cycle to look for the number of antral follicles. Both AMH and antral follicle count correlate very well and can give a prognosis. Women should consider having the ovarian reserve checked irrespective of chronological age by either having a blood test for AMH or an ultrasound scan for AFC before embarking on treatment. The treatment is going to provide the optimum environment for follicles to grow and for eggs to mature, to maximize the chances of the treatment being successful, which means collecting mature eggs that can be preserved in the later stages, survive and be suitable for in vitro fertilization and indeed minimize the risks as well as minimize the disappointment.
Egg-freezing – techniques
For a very long time, embryos, and eggs were frozen using a technique called slow freezing. The use of slow freezing had been shown to increase the damage to the cells, whereas the use of the more recent technique known as vitrification has been shown to maintain the structural integrity as well as the biological viability of the cells.
One of the studies published by Prof. Nardo and his colleagues at the ESHRE compared the use of slow freezing with vitrification. The team wanted to see if there was any potential disadvantage of using frozen oocytes compared to fresh oocytes. They looked at eggs that had been vitrified, and they found that the fertilization rate per egg was very much the same. They also looked at the clinical pregnancy rate, and they separated the studies that used donor eggs and those that didn’t use donor eggs, and again there was no difference. If the eggs come from young healthy fertile women, vitrification is not affecting the quality of the eggs and indeed, the chance of clinical pregnancy. It was concluded at the time that there was not a statistically significant difference in terms of clinical pregnancy between fresh and frozen eggs.
Another study published by Cochrane Review concluded that the intermediate outcomes, such as oocyte survival rate, fertilization rate and embryo quality appeared to be higher with vitrification compared to slow freezing. The percentage of high-quality embryos with vitrification compared to slow freezing is significantly higher. The number of oocytes that survive is higher with vitrification, it’s 91.8% compared to slow freezing, now at 61%. Looking also at the percentage of oocytes with abnormalities and comparing that to a control group, we can see that vitrification is very similar to the control group. Only 17% of oocytes have abnormalities with vitrification, compared to 39% of oocytes with slow freezing.
Oocytes vs embryo vitrification
One of the papers published shows that oocyte versus embryo vitrification for delayed embryo transfer has the same live birth rate. In a good lab with good technology and established techniques, freezing eggs will lead to the same live birth rate as freezing embryos.
Another study looking at the cumulative ongoing pregnancy rate achieved with oocyte vitrification, and cleavage stage (day-2, day-3 embryo) transfer without embryo selection presented that there is no statistically significant difference. The only difference that becomes obvious is looking at the female chronological age. The implantation rate using cryopreserved oocytes is about 30% in women under the age of 34, but 18% in women over the age of 38, and it’s only 9% in women aged 41 and older. The clinical pregnancy rate is 35.9% in women under 34, and there’s less than half in women under 41. The miscarriage rate increases with maternal age. The clinical outcome, according to frozen oocytes with fresh oocytes, is very much the same.
Looking at the study that assessed the performance of egg freezing in 7 different clinics across the United States that well identified as being egg banks shows that 6 out of the 7 egg banks used vitrification, and the majority of the egg banks would recommend the use of 6 oocytes to women and working on an egg donation cycle to achieve the best possible outcome.
Finally, another controlled study looked at the laboratory and also the clinical outcomes of oocyte vitrification in two age groups, aged 30 to 36, and 37 to 39. The clinical pregnancy rate in the age group 30-36 is 63.6% compared to 27.3% in the advanced age group. The implantation rate is significantly higher in the younger age group as compared to the more advanced age group. The reason for this is that the number of good quality eggs declines with age, so over the age of 35, it is a declining fertility phase of life, which has a significant impact on egg quality. The survival rate is also higher if there is a younger chronological age.
- oocyte freezing is a realistic approach to preserving fertility, it provides women who are not ready yet to start a family to postpone maternity
- women undergoing egg freezing should be made fully aware by healthcare professionals, and fertility physicians of the likelihood of success as well as the costs and the risks
- underlying ovarian performance is a very important determining factor.
- age is the other significant factor, so 35 years is probably the cut-off point to provide the best chance of success of the egg-freezing program.
- vitrification of eggs shows a significantly higher performance than slow freezing
- vitrification causes less damage to the eggs
- egg freezing is also an effective approach for egg donation cycles
- fertilization, implantation and clinical pregnancy rates are very similar for fresh and cryopreserved by vitrification eggs
- oocyte freezing is safe for obstetric and perinatal outcomes