It is 30 years since the first successful “frozen egg” pregnancy was conceived (
Chen, 1986
) and the difficulty and delay in reliably replicating Chen's original breakthrough was for many years the reason that oocyte cryopreservation was rightly considered to be a low-chance option for fertility preservation or extension. Early estimates suggested that 100 eggs were needed to get one live birth. For young women facing the near inevitable sterility of chemotherapy or radiotherapy, the prospect of freezing their eggs, if they were not in a relationship where embryo creation and cryopreservation was an option, even a low chance of genetic motherhood was acceptable. The introduction of new cryoprotectants that improved the freeze-thaw survival rates, and ICSI, which improved the fertilization rates, were welcome, but it was not until vitrification was applied to oocytes that the situation of egg freezing was transformed. Nowadays, it is probable that ovarian cortex freezing represents a superior and speedier option for cancer patients (ASRM Practice Committee, 2014
) but this approach is not widely available.There have been two European developments in recent years that have given the field of oocyte cryopreservation an unexpected boost. During the period when Italian law required all embryos created in a fresh cycle to be transferred and embryo cryopreservation was not allowed (
Benagiano et al, 2014
), there was intense pressure to improve the pregnancy rates from the supernumerary oocytes that could neither be fertilised nor transferred. These frozen-thawed oocytes made a valuable contribution to the cumulative pregnancy rate in Italy and demonstrated that “stopping the biological clock” for older would-be mothers could give them the opportunity of healthy pregnancies at an advanced age.The second development involving frozen eggs is the ascendancy of Spain as the principal provider of donor eggs to European women with age-related subfertility (
Ahuja, 2015
). Several excellent Spanish clinics now have “frozen egg banks” where young, vitrified, quarantined eggs are available to match any racial or physical characteristic required by the recipients. The pregnancy rates from these donor eggs, obtained from young women, are strictly comparable with those from fresh egg donation cycles.The success of these programmes has inevitably lead to increased enthusiasm for autologous egg freezing – not because of a deliberate intention to delay childbearing by the majority of highly-educated, professional women who seek egg-freezing – but because they want to have the opportunity to become a mother in a supportive, long-term relationship (
Smajdor, 2015
). In a paper in this issue of RBMOnline, Kylie Baldwin and colleagues (Baldwin et al, 2015
) confirm findings from studies in the US and Europe that absence of a partner is the commonest reason for “social” egg freezing, although anxiety about having a less than optimal reproductive “life-span” due to family or gynaecological history may also be relevant.The announcement by Facebook and Apple that they would cover the costs of “social” egg-freezing for their female employees has re-ignited the debate about whether egg-freezing represents the ultimate type of “family planning” for today's professional woman or whether the prospect of having 15 cryopreserved metaphase II oocytes in the freezer (the minimum number recommended) really does offer the opportunity to safely defer and delay motherhood until the right time arrives or the perfect partner hoves into view. However, the majority of women choosing to freeze their eggs have unfortunately already left it too late to have a realistic chance of achieving a live-birth from a single cycle of egg freezing (
Everywoman, 2013
). Just as with “fresh” eggs, successful pregnancies are more likely to be obtained using frozen young eggs – the early miscarriage rate from pregnancies achieved from older frozen eggs seems to be even higher than that of spontaneous pregnancies or “fresh” egg cycles of older women (Ubaldi et al, 2010
).The circumstances in which women choose to egg freeze often reflect their social situation, in which they have either failed to find a partner who wishes to parent with them, or a long-term relationship that they assumed was heading towards parenthood has failed, often because of commitment issues. It is unfair and unfortunate that at 38 (the modal age at which UK women seek egg freezing), she has two years to realistically achieve a healthy pregnancy whereas her similarly-aged partner has two decades. Baldwin and colleagues' paper demonstrates that currently women seeking “social” egg freezing are significantly committed to the conventional ideal family structure and regard single parenthood via the use of donor sperm as a poor last resort. By freezing their eggs they may believe they have “bought a little biological time” and the costs and small risks associated with the procedure may well be worth taking for that sense of empowerment. However, at the present level of efficacy of oocyte freezing, it is vital that women, especially if they are over 35, are made aware that their frozen eggs do not represent an insurance policy against age-related infertility.
References
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