What is PGD about?
This technology enables potential parents to select some characteristics of their unborn child. This enables them to avoid passing on a genetic disorder or disability, thus avoiding the dilemma of whether or not to terminate an affected pregnancy. Conventional In Vitro Fertilisation techniques (IVF) are used to create embryos. At around the eight-cell stage of development, one or two cells are extracted from the embryo, and the DNA analysed to check specific characteristics of the embryo. If free from the specific genetic disorder being tested, the embryo can be transferred to the uterus (womb), and pregnancy can continue.
Talking about PGD is important because it raises key questions such as:
• To what extent should morality, choice, and ability to pay be the determinants in this area of medicine?
• Does society have a duty to consider social and ethical issues, and to impose limits to clinical practice and individual choice?
• Is there an absolute distinction between genetic disease and disability, and normal variation?
When the cell for DNA analysis is removed, the embryo has 6-10 cells and is 3 days old.
If the tests show the embryo is free from a specific genetic disorder, the embryo is transferred to the woman’s uterus.
PGD (pre-implantation genetic diagnosis) involves genetic testing on a cell or cells taken from an embryo created by IVF.
The main alternative to PGD is pre-natal diagnosis plus selective abortion. Pre-natal diagnosis involves tests carried out on women who are already pregnant.
Since 1990, thousands of healthy babies have been born as a result of PGD tests.
PGD can test for many disorders that only affect male offspring. Female embryos may therefore be selected for, even if the exact condition can’t be understood. PGD then works by identifying and discarding the male embryos which could be affected by the disorder.
Families with a sick child have used PGD to create a child who could donate cord blood stem cells (or other tissues) for their sick sibling.
PGD is currently used to test for a growing number of genetic disorders, which are highly likely to be transmitted by the parents and are medically serious.
PGD is mainly used to test for disorders which are due to a fault in a single gene, such as cystic fibrosis and Huntington’s disease.
PGD allows families with a history of a genetic disorder to attempt to have children without the disorder.
Parents using PGD often have a child with a genetic disorder, and wish to have another child who isn’t affected.
For some conditions, PGD could be used to avoid having children who are carriers of a disorder, as well as those who would develop the condition.
All behavioural traits and most physical features depend on a combination of several genes and the environment.
PGD cannot be used to determine the sum of behavioural characteristics which make up a person.
PGD is already used for sex selection for social rather than medical reasons in the US, Middle East, etc.
IVF is physically, financially and emotionally demanding and involves drugs that may have side-effects.
Embryos that are not transferred can be disposed of, frozen for later use, donated to another infertile couple or used for research.
Each IVF cycle costs € 3 - 4000 and has an average success rate of up to 30% live birth per cycle (dependent on the woman’s age).
When embryos have grown for 3 to 5 days in culture (one fifth of a millimetre across), one or two embryos are transferred to the womb where they may implant several days later.
A test such as amniocentesis (where a needle extracts fluid that surrounds the baby) is now routinely offered to pregnant women at high risk of foetal abnormality.
In England and Wales in 2004, 1,900 abortions were performed because of a risk that the child would be born with abnormalities. The total number of abortions was 185,400.
The upper limit for abortion within select EU countries is 24 weeks into pregnancy. There is no limit for a foetus that shows severe abnormality.
Some pre-natal tests have a small risk (around 1% or less) of miscarriage or damage to the foetus.
In 2003, the UK Human Fertilisation and Embryology Authority recommended that the Government ban testing for sex selection for non-medical reasons.
When one partner has a balanced chromosomal translocation is normal - until he/she tries to have a child. When chromosomes join with the partner’s they make embryos with high risk for miscarriage or birth defects).PGD can detect this.
Human eggs are often chromosomally abnormal - and the risk increases with female age. About 25-40% of human embryos have some type of chromosomal abnormality. This increases to about 50% and higher for women in their 40s and over. PGD can test for this
When an embryo has reached the blastocyst stage and has between 30 and 100 cells (day 5 or 6 of development), a small number of cells can be removed for PGD to improve test accuracy.
Another PGD method is by testing the human eggs indirectly for genetic problems by testing the polar bodies (As an egg matures, it goes through a two-step division process, at ovulation and fertilisation; polar bodies are by-products of these divisions).
The abortion of abnormal foetuses is compulsory in China. Is this a slippery slope that we could be going down?
Do either regulatory or technical limits on PGD mean that it is impossible to create designer babies?
In the future, there is likely to be an increase in the number of conditions that can be diagnosed using PGD.
Using PGD increases ‘quality control’ in reproduction, and potentially will have eugenic applications and effects. Eugenics involves a deliberate effort to control the genetic makeup of human populations.
Is there a clear dividing line, when using PGD, between avoiding genetic disorders and eugenics? Eugenics involves a deliberate effort to control the genetic makeup of human populations.
Does society have a duty to consider the social and ethical issues, and to impose limits on clinical practice and individual choice?
‘Soon it will be a sin for parents to have a child that carries the heavy burden of genetic disease.’ (Bob Edwards, IVF pioneer).
Choosing not to transfer affected embryo is as bad as killing babies (Anon)
PGD and pre-natal diagnosis may encourage a consumerist attitude towards children.
Should health services be used to ‘select disability’, if disabled parents (e.g. people with deafness or dwarfism) wish to use the technique to have another child with the same disability?
It might be cheaper and more efficient to continue with prenatal screening, rather than invest funds in pre-implantation genetic diagnosis.
IVF success, and therefore PGD success, is related to the ability to pay for private treatment. This is intrinsically unfair.
Richer people have not just healthier babies, but in future may also have babies with better intellectual and physical abilities.
Parents spend time and money to create advantages for their children. Should society discriminate between different methods for doing so?
Priority for PGD should be given to families affected by genetic conditions.
Patients should be able to make their own decision on whether or not to have PGD, just as they do about other reproductive issues.
Counselling, information and support should be available for all. The medical system should support couples’ decisions about pregnancy and disability.
The avoidance of giving birth to disabled children results from public fear and ignorance about disability and lack of social support.
Disability is socially defined. Until recently, homosexuality was classified as a psychiatric disorder.
Many people born deaf regard themselves as a cultural and linguistic minority, and not as people with a disability.
The seriousness of a specific genetic condition that can lead to disability depends, not only on clinical judgment, but also on the views and resources of disabled people and families with that genetic condition.
PGD provides a solution (eliminating people with impairments) to a social problem (the way society treats disabled people).
There is a need to balance investment in developing new forms of genetic testing, with investment in the areas of counselling, information provision and training of medical personnel.
Genetic explanations for disability may reduce the attention paid to non-genetic ways of enhancing the quality of life of people with disabilities.
Health professionals vary widely in their knowledge of these subjects, so the information that patients receive is also variable.
Testing embryos at the blastocyst stage (day 5-6 of embryo development) allows for better embryo selection and more cells to be analysed to improve accuracy. However, it leaves less time for analysis, and decision-making before the transfer to the uterus.
Testing the egg is an accurate test with more analysis time and very little chance of harming any resulting embryo. However, the test cannot detect genetic problems which come from the father’s side or arise after fertilization.
Market is unregulated. It is possible and acceptable for couples to obtain a test for gender and personality traits on an embryo if they want it.
Controls on who can carry out genetic disease testing involving designated professional organisations and a voluntary code of practice. This is managed by an independent body. No licensing.
Only to be used for genetic diseases with serious medical consequences, not for gender or personality traits. Licenses issued for specific tests and conditions. Independent monitoring and evaluation.
Licensing and stringent monitoring and evaluation. In each country, an independent body (like The Human Fertilization and Embryology Authority in the UK) will license new tests and record each test carried out.