In theory, PGD could be used to look for any disease caused by a single gene, as long as a test has been developed for that gene. Until recently it was only offered in the UK for diseases also checked for during prenatal diagnosis (tests done when the woman is already pregnant).
But in November 2004 University College Hospital was given permission to use PGD to look for a gene which causes bowel cancer. Unlike other diseases PGD has been used to screen for, bowel cancer doesn’t affect people until they are adults. They are also investigating the possibility of using PGD for certain types of breast cancer.
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PGD can test for dozens of genetic diseases, including:
Achondroplasia
adenosine deaminase deficiency
alpha-1-antitrypsin deficiency
Alzheimer disease
beta thalassemia
cystic fibrosis
epidermolysis bullosa
Fanconi anemia
Gaucher disease
hemophilia A and B
Huntington disease
muscular dystrophy
myotonic dystrophy
neurofibromatosis type I
OTC deficiency
p 53 cancers
phenylketonuria
retino blastoma
sickle cell disease
spinal muscular atrophy
Tay Sachs disease
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PGD can be used to find out the sex of an embryo.
However, in the UK it is only legal to use PGD techniques for sex-selection to prevent a serious sex-linked disease. But some other countries allow the technique to be used for ‘family balancing’ – parents who already have one or more children of a particular sex can use PGD to choose an embryo of the opposite sex.
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Success rates for having a child from an IVF cycle followed by PGD varies but tend to follow standard IVF success rates. Therefore a pregnancy and an unaffected child cannot be guaranteed using this technique.
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(CGP, 2006)
There is a small error rate with PGD due to the complexity of testing a single cell in the laboratory. PGD is approximately 96-98% accurate and depends in part on the specific disease being tested. It must be stressed that this technology is still considered experimental. It cannot detect many genetic disorders at a time and cannot guarantee that the fetus will not have an unrelated birth defect.
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PGD has raised many ethical issues. On PGD: “Science has made it possible to do these things, but science can’t say whether we should do them.” (CGP, 2006)
However, “PGD does circumvent the problem of abortion, but it raises an interesting array of other practical and ethical issues.”
(Jeffrey R. Botkin, 1998)
By relying on the result of one cell from the multi-cell embryo, it is assumed that this cell is representative of the remainder of the embryo. This may not be the case, and on occasion, PGD may result in a false negative result, leading to the acceptance of an abnormal embryo, or in a false positive result, leading to the deselection of a normal embryo.
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When tests are carried out, there can be difficult decisions to make once the results have arrived. Here are some decisions and viewpoints:
- Some people prefer not to know if their baby has or has not got a genetic disorder: they are against PGD. However, is this fair on their partner or any future children they might have?
- Is it right for someone who is at risk of passing on a genetic condition to have children? However, is it fair to put them under pressure not to, if they decide they want children?
- If a test result is positive, is it right to terminate the pregnancy? Some people think abortion is wrong, whatever the circumstances.
- Is it fair on the parents to have a sick or disabled child, especially if they wouldn’t be able to cope? But does that child have less right to life than a healthy child? To some people, it does not matter what the child is like, they would love them all the same.
There are also some moral and religious issues that people may consider.
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Some people are completely for the use of PGD. They believe that no one is harmed during PGD, and everyone is helped, so it should be allowed. Why should anyone be forced to have a disabled child?
- Some people believe that PGD is always unnatural and wrong. They are concerned that we are going against nature by ‘playing God’.
- Other people think that terminating a pregnancy is wrong, no matter what. People should not destroy human beings; it does not matter if they have a disability or not.
- Religious people may be against PGD or abortion because their religion disallows it.
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A number of people are against the use of PGD for ‘designer babies’ or ‘sex selection’. This is completely unnecessary and PGD should only be used when it can really benefit someone – not just so someone can have a boy instead of a girl.
- Other people like the idea of PGD helping people, but are against the destruction of the unwanted embryos.
- People believe that Preimplantation embryos are too simple in development to have interests or rights, but they deserve respect as the first stage toward a new person.
Under these views PGD is ethically acceptable when done for good reasons, such as preventing offspring with serious genetic diseases.
It is also concerned that PGD is discriminatory; it is sending out the message that disabled people are seen essentially only by their impairments, with their potential attributes and social roles ignored. This is because the embryos which are affected by a disease are destroyed.
Another kind of concern is consequentialist. It arises from fears that increasing the frequency and scope of genetic screening of prospective children will move us toward a eugenic world in which children are valued more for their genotype than for their inherent characteristics, eventually ushering in a world of `designer' children in which genetic engineering of offspring becomes routine.
(John Robertson, )
I believe that PGD can be useful and beneficial in some cases, but unnecessary in others, i.e. I agree with PGD being used to prevent couples having children with genetic disorders, but disagree with PGD being used for sex selection.
Example Scenario 1
A couple want a baby, but they have discovered that they are both carriers of the genetic disease cystic fibrosis (CF). PGD would allow them to have a normal, healthy child by testing the embryos for the disease. The couple may not/would not want to cope with a child with the genetic disorder, and, with PGD, they could have a healthy child.
In this case, I agree with the use of PGD.
Example Scenario 2
A couple have 2 children already, both of them girls. They want the 3rd child they have to be a boy. PGD would allow them to have a boy instead of a girl by testing the embryos to see what sex they are.
In this case, I disagree with the use of PGD.
“We should not restrict the use of PGD to screen for severe genetic disorders.”
(Jason Christopher Roberts, Customizing Conception: A Survey of Preimplantation Genetic Diagnosis and the Resulting Social, Ethical, and Legal Dilemmas, Duke L. & Tech. 12th Revision, 2002)
I agree with this, but in addition I think the used of PGD for sex selection should be restricted.
Another viewpoint is:
“If PGD is acceptable to use it to prevent serious genetic diseases, why should it not be acceptable for any additional uses such as sex selection?”
I disagree with this, as I believe it is immoral to mess with a baby’s genes solely for the purpose of getting a boy instead of a girl, or vice versa.
In answer to the question “Should PGD be used to look for diseases such as cystic fibrosis or be used to choose the sex of a baby?”, I believe that it should be used to look for genetic diseases, but it should not be used to choose the sex of a baby.
However, there are limits and gaps in the evidence and data which support this conclusion, like the fact that I have not yet come across a real case study where PGD has been used for sex selection.
PGD is now almost proven to be valuable. Look at the graph below.
As you can see, with pregnancies after PGD has been used:
- The miscarriage rate has been reduced considerably;
- The implantation rate of embryos has increased drastically;
- The ‘take home baby’ rate has increased radically.
All of these changes are beneficial, so PGD has proven itself to be quite effective (despite the 2% rate of being unsuccessful).
(Graph taken from Reproductive Genetics Institute: )
Definition of PGD :
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The procedure of PGD :
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Quote on PGD procedure :
Luba Djurdninocic, "Pre-Implantation Testing,"
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CGP (Coordination Group Publications). (2006) GCSE Core Science OCR 21st Century, 1st Edition, Newcastle upon Tyne: Elanders Hindson Ltd
What is PGD used for? / Could PGD be used to choose the sex of a baby? :
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Diseases which PGD could test for :
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Advantages/Disadvantages of PGD :
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Reliability of PGD :
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Ethical issues :
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Jeffrey R. Botkin. (1998) Ethical Issues and Practical Problems in Preimplantation Genetic Diagnosis, 1st Edition, Volume 26
Jason Christopher Roberts. (2002) Customizing Conception: A Survey of Preimplantation Genetic Diagnosis and the Resulting Social, Ethical, and Legal Dilemmas, 12th Revision, Duke L. & Tech.
Evidence (Outcome of Pregnancies Before & After PGD) :
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Graph was slightly modified for use in this project.
