Egg-zactly!In 1978, the world saw the birth of the first IVF baby amid conflicting views surrounding the ethics of such treatment. Twenty-seven years later, assisted conception has made enormous progress but the same ethical questions continue, especially surrounding the area of pre-implantation genetic diagnosis (PGD). Read on to find out all you need to know about 'designer babies'.
Pre-implantation Genetic Diagnosis or PGD is a complex test which was developed in the late 1980s to identify embryos with genetic defects and chromosomal abnormalities to ensure only healthy ones are implanted in the womb. Also known as embryo screening, the test is performed before the embryo has even implanted into the lining of the womb and can only be done using embryos produced in the laboratory using in-vitro fertilization, regardless of whether or not the couple have fertility problems. How is it done?
PGD is offered to parents who are worried that they may pass a specific incurable genetic condition on to their child. They may already have had one or more affected children and usually one or both partners have been genetically screened and found to be a carrier. What can it look for?PGD was first used in 1988 and advances have been made in both the practical and ethical fields. It cannot be used to randomly look for potential abnormal genes as there are too many human genes to check. However, it can look for specific hereditary diseases such as;
These are conditions which only affect male babies so PGD is used to determine the female embryos and only implant them. PGD does not guarantee a healthy baby as it only looks for the specific genetic problem under investigation and does not detect other problems which may arise. What this means is that if PGD is being performed to detect cystic fibrosis, it will detect this but not other chromosomal abnormalities such as Down's. However, in August 2005, the Human Fertilisation and Embryology Authority (HFEA) granted licence for doctors to screen for a rare form of eye cancer called retinoblastoma. The move has caused fresh ethical debate as the condition is rarely fatal and is curable in 95 per cent of cases. But, Dr Paul Serhal, of the assisted conception unit at UCH, said it is worth screening for because people with retinoblastoma have a 50 per cent chance of developing another cancer at a later point in life. Is it safe?There are risks common to other aspects of IVF such as hyper-stimulation, multiple pregnancies and ectopic pregnancies. For reasons not fully understood, there is a low implantation rate of healthy embryos, currently at around 20 per cent. This is thought to be because many good quality embryos are rejected. There have also been concerns that the removal of one or two cells at the 8-cell stage could be in some way damaging to the baby. However, Alan Handyside, who reported the world's first PGD with Professor Robert Winston at Hammersmith hospital in 1990, says embryos appear to be undamaged by having cells removed at such an early stage and, as long as half the cells survive, the embryo will usually develop healthily. In 1997, the European Society of Human Reproduction and Embryology (ESHRE) PGD Consortium was established by Dr Joyce Harper to gather detailed information about PGD cycles. In August 2004, the results of their study of 754 babies born after PGD showed that abnormalities were no more common than in the general population, at about 0.4 per cent for Down's syndrome or spina bifida, and up to 4 per cent for medical conditions such as cleft palate. Dr Harper says, "Several clinics are following children for a few years to check that their brain development and general health are unaffected. As far as delivery, birth weight and malformations at birth are concerned, there's no difference seen at the moment." So what are the objections?Some people believe screening and destroying 'unhealthy' embryos is unethical. There is also the argument that many inherited diseases do not become apparent until a person is in their 30s or 40s and potentially a cure could be found by then. However, the biggest worry is 'social screening', where people can determine the sex of their baby for social reasons rather than medical reasons. Although illegal in the UK, some countries do practice this kind of PGD. There is also the concern that this may extend to screening out 'undesirable' social traits such as certain sexual orientations. What's the future?The Pre-implantation Genetics Diagnostic International Society (PGDIS) says, "Recent advances in pre-implantation genetic diagnosis (PGD), and the widening success gained with IVF to alleviate infertility offer highly positive outlooks for future work in the whole field of reproductive medicine." Recent advances have provided the ability to determine genes which can suppress tumours and senile dementia and now new technologies have pinpointed thousands of genes in laboratory mice embryos, and the same techniques could soon be used on human embryos. It is hoped that miscarriage due to chromosomal problems in the embryo will continue to reduce using this technology along with the number of couples who have to face terminating a pregnancy following routine prenatal diagnosis. Where to next?
|
