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Pre-implantation genetic diagnosis (PGD) & haplotyping (PGH)

Current status; Objections; Advantages

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Current status of the PGD procedure:

Initial PGD research was performed in the UK during the late 1980s. It remains a rare procedure that is only available in a few clinics worldwide. It can be used to detect a few hundred disorders and diseases. There is the potential that it will detect many hundreds eventually. 1

According to the Sher Institute:

"By the year 2000, more than 1500 couples had participated in PGD clinical trials, which are ongoing in several centers around the world, and more than 1000 PGD/IVF cycles had been performed, In virtually all of these cases, PGD was followed by early prenatal genetic diagnosis to eliminate the risk of misdiagnosis through PGD. Several such errors in PGD have been recorded to date. These pregnancies were all terminated, electively." 2

According to Anuja Dokras of the Yale University School of Medicine:

"This technique is currently available to couples whose offspring are at a high risk (25-50%) for a specific genetic condition due to one or both parents being carriers or affected by the disease. Also the genetic code associated with the condition must be known in order to allow diagnosis. Currently it is not feasible to routinely screen women at lower risks, such as women over age 35 for Downs Syndrome..." 3

An article in The Guardian, a UK newspaper quotes The Human Fertilisation and Embryology Authority, (HFEA) as describing PGD as "a physically and mentally demanding process which does not bring any guarantee of success." With PGD, the live birth rate is probably even lower than the average 17% IVF success rate, and the whole procedure is considerably more expensive. 4

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Objections to the PGD procedure:

bullet Conservative Christians and others typically people believe that human personhood begins at conception. This means that any destruction of an embryo is equivalent to the murder of a human person. There are a number of concerns that they have about PGD:
bullet The cell that is removed could conceivably, under the right conditions, develop into a fetus on its own. But the testing will destroy it.
bullet The fertilized cells that are not implanted are usually destroyed, as in in-vitro fertilization procedures.
bullet If a genetically defective cell is found, then the entire embryo from which it was extracted is destroyed.
bullet Dr. Patricia Baird, a geneticist who led the Canadian Royal Commission on New Reproductive Technologies said: "Because there is so much money involved, there is a real danger of premature, unwise application of this procedure." We find this comment confusing. The procedure would cost in the vicinity of $4,500 to $7,000 in US funds. One might argue that because of the high expense involved, the procedure would only be applied in unusual cases after much careful thought.
bullet A genetically defective fertilized egg, if allowed to mature and cause a live birth, it would not necessarily generate a disorder or disease in the individual. Various genetic variations (called alleles) have a penetrance factor, which is a measure of their effectiveness or power. For example, the allele which causes Huntington's Disease has a 100% penetrance: if you have the allele, you will certainly develop the disease. But other genetically determined conditions have a much lower penetrance: left handedness is only about 15%; the gene(s) that cause homosexuality have a penetrance factor that is about 67% -- between that for Huntington's and left-handedness. Thus, many embryos would be killed which would never have caused a disease or disorder.
bullet Some genetically caused diseases only develop symptoms when the person is in their 30's or 40's. By that time, a cure might have been found.
bullet The procedure could be the start of a slippery slope. Perhaps embryos would be eliminated that might leave the individual at higher risk for heart disease, or stroke, or obesity, etc. And there is the possibility that the procedure could be used to eliminate female embryos, or embryos that would grow into adulthood with a minority sexual orientation -- bisexuality or homosexuality. This is an ironic situation: religious conservatives, who are most likely to have a strong preference for a baby that would mature as a heterosexual adult, would be exactly the group who are most opposed to PGD which has the potential to eliminate homosexuals at the embryo stage.
bullet Some religious and social conservatives are worried that the technology could lead to the creation of babies to be used for spare parts.
bullet CitizenLink, a service of Focus on the Family Action -- a fundamentalist Christian group -- published a brief article objecting to abortions triggered by the discovery of Gaucher disease in an embryo or fetus. They describe it as "a treatable genetic disorder." Their concern would also apply to cases where the disease is detected using PGD. They believe that parents are sometimes not given a full understanding of the disease. Focus/Action wrote:

"Dawn Vargo, associate bioethics analyst at Focus on the Family Action, said it's just the latest example of the ethical problems that can be associated with prenatal screening. 'This study provides evidence that parents who receive screening on complex genetic diseases may choose to abort their children based on misinformation or lack of information'." 7

According to Wikipedia, Gaucher's disease:

"... is the most common of the lysosomal storage diseases. ... Symptoms may include enlarged spleen and liver, liver malfunction, skeletal disorders and bone lesions that may cause pain, severe neurologic complications, swelling of lymph nodes and (occasionally) adjacent joints, distended abdomen, a brownish tint to the skin, anemia, low blood platelets and yellow fatty deposits on the sclera. Persons affected most seriously may also be more susceptible to infection. ... The currently existing treatment of Gaucher's disease, Cerezyme (imiglucerase for injection), costs up to $550,000 annually for a single patient and the treatment should be continued for life." 8

Various forms of the disease occur in about 1 in 25,000 live births. Some versions of the disease can cause serious convulsions, mental retardation, dementia, etc.

Focus did not mention what "misinformation or lack of information" parents were provided with.

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Advantages to the PGD procedure

bullet Most genetic testing now is done through amniocentesis when the fetus is 12 to 16 weeks old. The results are typically available after a wait of an additional three weeks. In this, a sample of the amniotic fluid is drawn from around the fetus. A floating cell from the fetus is then found and analyzed. If the analysis shows that the fetus is genetically defective, then the parents have the option of aborting the fetus. Essentially all couples in North America and the UK do elect to have an abortion. Amniocentesis is be far more distressing than Pre-Implantation Genetic Diagnosis to most couples, because it is performed at a time in gestation when the fetus is so fully developed. The PGD technique is performed before pregnancy begins; it would avoid much of the stress and moral conflict in most couples. However, strongly pro-life couples may not differentiate morally between the destruction of a three-month fetus and an eight-cell embryo; they may consider both to be fully human persons.
bullet Some adults who know that they are carriers of a genetically transmitted disease decide use contraception in order to not have children. The Pre-Implantation Genetic Diagnosis procedure allows them to have a child with full assurance that it would not be carrying that disease. (Of course, the child could be born with other malformations, diseases and disorders that were not tested for.)
bullet If the procedure became widespread, the incidence of many diseases would be reduced, since few people with the disease would be born and later have children.
bullet The procedure could significantly reduce the cost of medical systems in North America. Treatment of some genetic diseases can easily cost millions of dollars over the lifetime of a single individual.

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The following information sources were used to prepare and update the above essay. The hyperlinks are not necessarily still active today.

  1. "Fact sheet: Preimplantation Genetic Diagnosis, American Society for Reproductive Medicine, at: This a PDF document. You can obtain a free software to read this type of file from Adobe.
  2. "Pre-implantation genetic diagnosis (PGD) A commentary on its utility and potential value," at:
  3. Anuja Dokras, M.D.Ph.D., "Pre-Implantation Genetic Diagnosis", Pre-Implantation Genetic Diagnosis, Vol.1 No.5. See:
  4. Sarah Boseley, "Public views on embryo genetic testing sought,"
  5. "Screening for Treatable Genetic Disorder May Lead to More Abortions," CitizenLink, 2007-SEP-19, at:
  6. "Gaucher's disease," Wikipedia, 2007-SEP-03, at:

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Copyright 1999 to 2007 by Ontario Consultants on Religious Tolerance
Latest update: 2007-SEP-20
Author: B.A. Robinson

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