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Pre-implantation Genetic Diagnosis

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What is PGD about?

Author / translator Andrea Bandelli

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?

Created 2 February 2010
Last edited 20 June 2018
Topics Health, Science

Policy positions

Policy position 1

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.

Policy position 2

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.

Policy position 3

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.

Policy position 4

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.

Story cards


Adam Nash was born in the USA in 2000. This was the first time that PGD had been used both to screen for a disease and to ensure a tissue match in a sibling. PGD was carried out so that he would be free from a genetic disorder called Fanconi’s anaemia, from which his six-year old sister Molly suffered. This disorder can affect many systems in the body but frequently leads to cancers, including Leukaemia. Umbilical cord cells taken from Adam were then used to successfully replace her failing bone marrow. Without this treatment, she would have died within a few years.

Adam and Molly Nash

Spinal Muscular Atrophy (SMA) is a genetic condition resulting in muscle wasting which can cause death in infancy. For some sufferers, such as five-year-old Kate Snapes, SMA means that she will never be able to walk. Kate’s parents wanted to have more children, but because of the one in four risk of producing another child with SMA they were deeply cautious until an answer was offered by PGD. The couple used PGD technology to successfully select ‘healthy’ embryos for transfer. The twins Isabelle and Esther were born without the SMA condition in November 2001.

The Snapes Twins

In 2002, the UK Human Fertilisation and Embryology Authority (HFEA) allowed the Hashmi family to use PGD to create a ‘donor’ sibling for their three year old son Zain, who suffers from a rare and dangerous genetic blood disorder called thalassaemia which reduces his ability to transport oxygen around his body. Cells from the umbilical cord of the PGD selected baby could be used to provide a cure for Zain. The idea of a ‘donor’ child is controversial, but as Mrs Hashmi argues, when Zain gets older ‘He will know he is going to die. How is he going to feel if he knows something could have been done to save his life?’

The Hashmi Family

Several countries allow couples to plan the gender of their unborn child using PGD. Gender selection is only allowed in the UK to help prevent a genetic disorder. Louise and Alan Masterton lost their three year old daughter Nicole in a tragic fire accident. The family wanted to use PGD to create another daughter, to balance a four son family. This was refused by the Human Fertilisation and Embryology Authority (HFEA). A spokesman commented, ‘British society is not yet prepared to accept this … my view is that society will accept this, but it is not going to happen now.’

The Masterton Family

In 2002, the Reproductive Genetics Institute in Chicago used PGD for the first time to ‘screen out’ embryos carrying a cancer-causing mutation. The Institute were helping a couple from New York to have a baby without running the risk of passing on Li-Fraumeni Syndrome (which was carried by the father’s family) which leads to an 80-90 percent chance of developing cancer. The lead doctor commented that the decision on whether to test embryos should be up to the doctor and the patient. ‘Government regulations always backfire’, he said.

Li-Fraumeni Syndrome

Mia (not her real name) has several family members who have developed bowel, stomach or womb cancer at an unusually young age. She was therefore offered tests, after which she was told that she has inherited a genetic change that means she has a 60-90 per cent lifetime risk of developing some type of cancer. She now has regular check-ups to pick up any early warning signs.

Mia says that getting the test results has affected her life in several ways. For example: ‘If I have a child, I might pass on that [defective] gene to my child.’


These are extracts from a diary that Leah wrote about her experience of PGD in the UK Guardian newspaper in 2000:
“I'm buying a baby on MasterCard. PGD is rarely funded. I am going to have to cough up £2,500.”
“So convinced was a friend by this misrepresentation (about ‘designer babies’) that when I told her my forthcoming twins are a boy and a girl, she said: ‘Oh, so that's what you chose!’ - as though PGD was rather like going to the supermarket. All I chose is embryos that wouldn't have a catastrophic chromosomal disorder and die.”

Leah Wild

Anna is the central character in the novel My Sister’s Keeper, by Jodi Picoult. When she asks how babies get made, her parents, “explained that they chose little embryonic me, specifically, because I could save my sister Kate. It made me wonder what would have happened if Kate had been healthy.”

“Kate has acute promyelocytic leukemia. When Kate needs leukocytes or stem cells or bone marrow to fool her body into thinking it's healthy, I'm the one who provides them. Nearly every time Kate's hospitalized, I wind up there too. I'm not sick, but I might as well be.”

Anna Fitzgerald


Chinese policy

The abortion of abnormal foetuses is compulsory in China. Is this a slippery slope that we could be going down?

Designer babies

Do either regulatory or technical limits on PGD mean that it is impossible to create designer babies?

Future potential of PGD

In the future, there is likely to be an increase in the number of conditions that can be diagnosed using PGD.

Designer populations

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.

Where do we draw the line?

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.

Society’s role

Does society have a duty to consider the social and ethical issues, and to impose limits on clinical practice and individual choice?

Strong opinions

‘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)

Shopping for genes

PGD and pre-natal diagnosis may encourage a consumerist attitude towards children.

Selecting disability?

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?

PGD – is it cost effective?

It might be cheaper and more efficient to continue with prenatal screening, rather than invest funds in pre-implantation genetic diagnosis.

PGD – availability

IVF success, and therefore PGD success, is related to the ability to pay for private treatment. This is intrinsically unfair.

Better babies?

Richer people have not just healthier babies, but in future may also have babies with better intellectual and physical abilities.

Gaining an advantage

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.

Who decides?

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.

Avoiding disability

The avoidance of giving birth to disabled children results from public fear and ignorance about disability and lack of social support.

Disability defined

Disability is socially defined. Until recently, homosexuality was classified as a psychiatric disorder.

Is deafness a disability?

Many people born deaf regard themselves as a cultural and linguistic minority, and not as people with a disability.

How serious?

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 – a solution?

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.

Quality of life

Genetic explanations for disability may reduce the attention paid to non-genetic ways of enhancing the quality of life of people with disabilities.

Professional knowledge

Health professionals vary widely in their knowledge of these subjects, so the information that patients receive is also variable.

PGD test at the blastocyst stage

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.

PGD test at the polar body stage (egg testing)

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.

Cell removal from an embryo

When the cell for DNA analysis is removed, the embryo has 6-10 cells and is 3 days old.

Embryo Transfer

If the tests show the embryo is free from a specific genetic disorder, the embryo is transferred to the woman’s uterus.

What is PGD?

PGD (pre-implantation genetic diagnosis) involves genetic testing on a cell or cells taken from an embryo created by IVF.

Technical alternatives to PGD

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.

PGD babies

Since 1990, thousands of healthy babies have been born as a result of PGD tests.

Gender and disease

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.

Donor siblings

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.

Current PGD use

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.

Testing for Single Gene Disorders

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.

Family history

PGD allows families with a history of a genetic disorder to attempt to have children without the disorder.

Parents choosing PGD

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.

Nature and nurture

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.

Sex selection

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.

Unused embryos

Embryos that are not transferred can be disposed of, frozen for later use, donated to another infertile couple or used for research.

IVF costs and success rates

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).

Embryo Transfer

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.

Tests during pregnancy

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.

Abortion legislation

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.

Test risks

Some pre-natal tests have a small risk (around 1% or less) of miscarriage or damage to the foetus.

Sex selection

In 2003, the UK Human Fertilisation and Embryology Authority recommended that the Government ban testing for sex selection for non-medical reasons.

Carriers of chromosomal translocations

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.

Age factors

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

PGD at the blastocyst stage

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.

PGD with polar body analysis

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).

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