Whatever doubts there may be about the safety of cryopreservation, it is one of the most important advances in IVF technology. The storage of eggs for women having cancer therapy that may produce an early menopause is one advance. Another is egg donation.
In the last ten years, there has been a rise in interest in helping older women preserve their fertility. In nearly all developed societies, women are leaving child-bearing later. In the UK the average age of a woman in her first pregnancy is now over 30. Many find themselves struggling with fertility problems as a consequence. In response to this, younger women are considering having some of their own eggs frozen until they find their ideal partner.
The first baby produced as a result of egg freezing was born in Singapore in 1987, using a technique established for embryo cryopreservation. However, until quite recently egg freezing was regarded as too risky. It seems that the serious genetic effects first reported by scientists have been overcome by using either the slow cooling procedure or freezing quickly by vitrification. That is not to say that freezing eggs do not cause unwanted changes. Indeed, it is striking how many frozen eggs are damaged or not viable after thawing.
A research team in Leicester, UK, led by Dr. Meelam Potdar have made a comprehensive review of what has been published on egg freezing. The team evaluated 21 different studies that examined the results of over 11,000 human eggs. There is no doubt that egg freezing is a good deal less successful than optimistic articles in newspapers and women’s magazines (or claims by some clinics) would suggest. The results using vitrification seem marginally better with just under 90 percent of the eggs survived thawing, of which around 75 percent were capable of being fertilized, but only 7 percent of those developing into embryos gave rise to a pregnancy. Finally, approximately 20 percent of the pregnancies ended in miscarriage. Somewhat surprisingly, these authors conclude that egg freezing is effective and safe, but I am unconvinced.
These figures are born out from data recently obtained from the UK’s HFEA (Human Fertility and Embryology Authority). Up to 2012, 2,262 women had a total of 20,465 eggs frozen. In all 243 women freezing their eggs or having frozen egg donation were treated and there were 253 treatment cycles. The result of all these frozen eggs is that there have been 21 pregnancies (around eight percent), but the number of live births is not recorded. Given that most of these women were relatively young when their eggs were taken and stored, this is not an impressive success rate. Egg freezing does not seem a suitable treatment for women in their later thirties as they generally have eggs of less good quality and don’t respond as well to ovarian stimulation. It’s unlikely that in this group, given current technology, the results would be anything like as good as eight percent.
If egg freezing could be perfected it would be very valuable and could have enormous advantages over embryo freezing. Frozen embryos raise ethical issues. Unfertilised eggs carry much less moral status, and their disposal should, therefore, be easier. Egg freezing could paradoxically, also be safer because, after thawing, a frozen embryo is more or less immediately transferred to the uterus, offering little opportunity to check whether it is growing normally. By contrast, a thawed egg has to be fertilised, which in itself is one test of normality, then there is the opportunity to observe the growing embryo. An important result of this research, however, is that a number of different ways of assessing embryo quality are being developed.
Despite countless breakthroughs in medical science, we still do not understand why some pregnancies will end in tragedy. For most of us, having a child of our own is the most fulfilling experience of our lives. All of us can imagine the desperation and sadness of parents who lose a baby, and the life-shattering impact that a disabled or seriously ill child has on a family.
Professor Robert Winston’s Genesis Research Trust raises money for the largest UK-based collection of scientists and clinicians who are researching the causes and cures for conditions that affect the health of women and babies.
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