In vitro future

 
 

Shaila Zaver explores the newest developments in the field of In Vitro Fertilisation.

It was just over 30 years ago that the world marvelled at Louise Brown, a child famous before she took her first breath. She was the world’s original test tube baby – the first viable child conceived by In Vitro Fertilisation. Since then, over 3.5 million people have successfully followed suit.

Since the birth of Brown in 1978, IVF has been a major form of treatment for infertility – when couples are unable to conceive naturally. Quite simply, the procedure unites the female’s egg with the male’s sperm, in a Petri dish. The resultant zygote – the beginning of a human life – is allowed to grow, and eventually implanted in the female uterus.

Prior to egg retrieval, a woman undergoes hormonal therapy with fertility drugs to stimulate the development of ovarian follicles, which eventually become eggs. Just before ovulation the eggs are removed from the ovaries, and placed with the selected sperm in a fluid to facilitate their union. Following a brief incubation period, the fertilised eggs that appear most viable are implanted within the woman’s uterus, with the hope that one survives.

With such an astounding number of successes, it may seem surprising that only one quarter of all IVF attempts using fresh eggs yield results. Even fewer with frozen eggs are successful.

Yet, there is new hope for those who have struggled for years with ineffective rounds of IVF. A novel method has been developed, with the ability to check the viability of eggs before they are implanted in a woman’s uterus. And, in just under two months, the world’s first baby conceived by this technique will be born.

So why is it that IVF so often fails? The problem is that up to 50 per cent of the eggs produced by a woman’s ovaries contain chromosomal abnormalities that are not able to produce a viable foetus. This percentage steadily increases with age, rising to 75 per cent by the time she reaches 40.

Until recently, we have been unable to examine the chromosomes within an egg to see if they are healthy without damaging the egg and rendering it useless for conception. It is only now that such a screening technique has been developed – one that doctors hope will double the number of successful pregnancies.

“It may seem surprising that only one quarter of all IVF attempts using fresh eggs yield results”

How exactly does this procedure work? When human eggs begin to develop, they contain 46 chromosomes. Through the process of maturation, 23 of these chromosomes are retained within the nucleus of the egg, and the other 23 are stored as a polar body, a dispensable bi-product that eventually disintegrates.

The 23 chromosomes within the polar body are identical to those within the egg. The new technique, known as Array Comparative Genomic Hybridisation, utilises this trait. The polar body of an egg is extracted using a laser scalpel, and the chromosomes are analysed. If they prove to be healthy and viable, the egg is thought to be the same, and implanted in the woman’s uterus following fertilisation.

This procedure, developed by the UK’s CARE Fertility Clinic, can be of extreme value to those who have suffered through countless rounds of IVF without any success. Such was the case for an unnamed 41-year old female, who underwent 13 rounds of IVF, only to have to endure two miscarriages and an ectopic pregnancy. After using array CGH, she is now pregnant in her third trimester, with only two months remaining in her pregnancy.

While 13 attempts at IVF may be extreme, the majority of women do require several rounds before they achieve success. And this success comes at a high cost – up to €4000 per round. The additional €2000 for array CGH may prove to be worthwhile for many couples who may achieve success with far fewer rounds.

With conventional IVF procedures, the high failure rates mean that multiple embryos are usually implanted simultaneously in the hope that one will persist. This often results in the birth of twins, triplets, or even octuplets, as was seen recently in California.

While it is recommended – both in the UK and the US – that no more than two embryos be implanted, a mother’s desire for a successful pregnancy may occasionally overrule these guidelines, which are not set in stone. Unfortunately, infants of multiple-births are at a greater risk of being born premature. This has subsequent complications, some of which can be fatal. Array CGH bypasses the risk of multiple births simply by implanting fewer embryos, while improving the success rate.

While the benefits of such a procedure are significant, the ethical dilemmas it poses cannot be ignored. Once you begin examining the viability of eggs, at what point do you draw the line? What genetic traits could you potentially screen for?

Theoretically, this procedure could allow embryos to be cast aside for something as trivial as eye colour. As is the case with conventional IVF, eggs that are not considered to be the ‘best’ are simply discarded as biological waste, which many people feel directly violates the sanctity of life.

Although the application of array CGH in IVF is mired in moral complications, its potential benefits cannot be overlooked. This technique is capable of helping women who have been unsuccessful with natural conception or conventional IVF.

There continues to be room for improvement, for the further refinement of current procedures to make them even better and more successful. Dr Simon Fischel, director of the CARE Fertility group, says that: “Ultimately we could reach the holy grail of one cycle of IVF, one egg, one embryo and one baby.”

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