Renee and David Abshire are both carriers of Tay-Sachs disease. Their daughter Maigon Nicole died at age three from the cruelly debilitating disease. They wanted another child but they couldn’t face the possibility that their new baby would suffer the same fate as their daughter. But in 1994, thanks to a new procedure in reproductive technology called pre-implantation genetic diagnosis, or PGD, the Abshires conceived and gave birth to a healthy little girl. The Abshire baby was the first successful birth of a child screened for Tay-Sachs.(2) The concept behind PGD is fairly simple: to fertilize an egg in vitro and then screen for genetic disease before implanting it in the womb. Thus couples at risk of producing genetically diseased children can be assured that they have conceived a healthy child. They also circumvent the dilemma of having to abort a child if the traditional pre-natal screenings of amniocentesis and chorionic villous sampling, performed in the 16th and 10th weeks of pregnancy respectively, come back positive for genetic mutation. Scientists can currently screen for a host of genetic disorders which include cystic fibrosis, Duchenne’s muscular dystrophy, myotonic dystrophy, Lesch-Nyhan syndrome, hemophilia A and Tay-Sachs among others. (6)
The process begins by giving a woman a "cocktail" of ovarian stimulants that usually includes gonadotropins in combination with gonropin releasing hormone analogs, causing multiple eggs to be released.(4) More than one egg is needed because the chances of producing a viable fetus increase with the number of eggs that the scientists have to work with. If one is testing for an autosomal recessive trait such as Cystic Fibrosis and both parents are carriers, then Mendelian genetics dictates that after fertilization approximately one quarter of the embryos will be afflicted with the disease. If screening is performed for a dominant disease such as Huntington’s Disease the number of viable fetuses will be reduced by about 50%. After the multiple eggs are produced, they are removed from the woman’s body through a process of oocyte aspiration. The eggs are then placed in a petri dish within a culture media and fertilized in vitro with the father’s sperm.
The fertilized eggs are allowed to grow until they reach the 8 cell blastocyst stage. A biopsy is then performed on the preembryo where one or two of the eight cells, called blastomeres, are removed. (4) The blastomeres are surrounded by an outer membrane known as the zona pellucida which holds the cells together and gives the preembryo its structural integrity. In the biopsy, the zona pellucida is either cut open with a sharp instrument or it is degraded with acid Tyrode’s Solution, and one or two cells are sucked out using a pipette. (4) Interestingly the preembryo is not effected by the micromanipulation at this stage and it can proceed to develop normally despite having lost as much as a quarter of its total mass. (3)
The next step involves screening the DNA of the biopsied blastomeres. In cases dealing with X-linked diseases such as hemophilia or Duchenne’s muscular dystrophy, the cells are analyzed to determine sex and only female embryos are implanted. Though females may carry the mutant gene on one of their X chromosomes, it is generally only males that will actually develop the disease. When the disease is not X-linked, then it is necessary to actively examine the DNA for genetic flaws.(2) Because the DNA retrieved from the blastomeres is so minute, it is replicated using polymerase chain reaction, or PCR, in order to allow scientists to work with the DNA and try to locate a specific gene.(1) This method of PCR is used when the embryos are at risk of developing a disease that is caused by a single-gene defect such as cystic fibrosis or sickle cell anemia. (4) In other cases where the disease arises from chromosomal abnormalities, a process called fluorescent detection of in situ hybridization, or FISH, is used.(7) Essentially it involves injecting fluorescent DNA probes that are made to home in on certain mutations. Once an embryo passes the various types of screenings and is deemed normal, it is injected back into the uterus where it has a chance to implant and progress to a pregnancy.
The process of PGD is far from perfect and the success rate of the procedure is rather low. The birth rate per IVF treatment in the United States is 14% and 12.5% in the United Kingdom.(7) One of the reasons for the poor success rate is the fact that the longer the preembryo spends outside of the womb in the relatively inferior conditions of the culture media, the less chance it has to implant itself successfully in the uterus. It is thought that if there were some way to perform the biopsy on a blastocyst during a more advanced stage, like 5 to 6 days after fertilization instead of the 2 to 3 days it takes for the preembryo to reach the 8 cell stage, then it would be stronger and have a higher chance of successful implantation. This has lead researchers to develop the method of uterine lavage in which the embryo is fertilized naturally in vivo, taken out before it has a chance to implant, and then returned to the womb only if it passes the tests and is healthy.(6) Uterine lavage has only met with very limited success however and the rates of a impregnation are in fact lower than with traditional in vitro fertilization.(5)
The issue of PGD is a very controversial one that has raised a myriad of ethical questions and moral dilemmas. The idea of genetically screening embryos for desirable traits tends to conjure up images of eugenics and terrifying visions of a futuristic society ripped from the pages of Huxley’s Brave New World or Hollywood fiction. Much of the opposition toward PGD results from a belief that though PGD is currently used to eliminate serious genetic disorders, it may one day be used to select frivolous traits or may be used in processes of genetic enhancement. This slippery slope argument however is not a convincing one. There is a vast difference between testing for cystic fibrosis and testing for eye color. Both the results and the motivations behind the technology are essentially different. This having been said however, one must admit that though the slippery slope argument is logically flawed, PGD does crack open the door, albeit slightly, for the possibility of future screening for traits that are not necessarily diseased. It does so by setting a precedent for any kind of genetic screening prior to implantation. The two scenarios are linked in that they involve examining DNA and making a value judgment on the traits observed.
Additionally, it seems naive to think that PGD technology will never be used for ethically questionable motives. When pre-natal screening techniques such as amniocentesis arose, they were at first only administered to women who had a higher risk of producing a genetically diseased baby. Now the vast majority of doctors administer an amnio at the request of the patient even if her embryo is not at a higher risk for genetic problems.(6) The point is that it is very difficult to draw steadfast lines in medicine and ethical boundaries are bound to constantly shift. A procedure such as PGD, by its very nature, favors such shifts. In certain cases, when there are two viable sets of embryos, one of males and one of females, both of which have passed the genetic screenings, it is the parents who decide which embryos they want implanted.(5) It is now no longer a question of disease but rather of sex and the boundary has already shifted. I would argue that the line between wanting to have a healthy baby and wanting to have the healthiest possible baby is extremely fine, especially considering the emergence of germ line technology that could facilitate such genetic enhancements.
In a 1990 poll, 12% of women said that they would terminate a pregnancy if the fetus possessed a hypothetical gene for untreatable obesity. (6) Another survey indicates that at least half of the geneticists in the U.S. have had a request for sex selection, and some IVF clinics have reportedly begun offering to select embryos of a particular sex even if there is no history of a sex linked disease.(6) Such alarming public attitudes, coupled with the fact that many IVF clinics are privately funded and there is no over-arching organization with any real power to enforce ethical standards, make it seem that a future increase in frivolous trait selection is not so far fetched. After all, profit is a powerful motivation for these clinics.
In considering the moral implications of PGD, we should also examine our conceptions of disease. Certain cases are more clear cut than others. Few would argue that a condition such as Tay- Sachs is not a disease. But what should we make of a couple in England who underwent PGD to screen for a gene that may increase the chance of developing cancer later in life? (1) Are we justified in nullifying 45 years of a life because of the prospect of Hotchkin’s disease? Another thing to consider is our attitude as a society to those very visible diseases such as Down Syndrome. In a recent lecture, C. Everett Koop made an excellent point that disease is a very subjective concept. When we perform genetic screenings, we are making a value judgment as to the worth of an individual’s life that is afflicted with the disease. PGD is absolutely a from of eugenics. Koop’s lecture makes one realize that having a genetic condition does not prevent one from enjoying a life that is just as rewarding as that of anyone else. The fact is that we know an incredible amount about the biological make up of human beings. But we really don’t know very much at all about what it is that makes us human. If anything, our contact with these supposedly defective individuals serves to make us more human.
Perhaps the most attractive aspect of PGD to perspective parents is that it allows them to circumvent the entire issue of aborting a fetus that is already growing within the mother’s womb. However I would submit that the differences between selective abortion and PGD are not as great as might first appear. The traditional conservative pro-life position objects to abortion because it is the destruction of what will potentially develop into a life. On these grounds, PGD is just as morally objectionable as abortion because it too involves the destruction of embryos that are deemed unfit to be implanted. Indeed it is arguably worse because it entails the intentional creation of more than one embryo to produce only one life. Others would argue that it is morally worse to abort a fetus than an eight cell preembryo because the fetus has already achieved certain developmental milestones. On this point I would have to agree. However, I believe that part of what one finds objectionable in the abortion of a fetus is the feeling that one is somehow killing a sentient being. It has been proven that brain function in the fetus does not arise until 20 to 22 weeks and a sentient state arises at 22 to 24 weeks. (5) An amniocentesis can accurately be performed as early as the 16th week of pregnancy.(4)
One of the things that PGD does circumvent is the agonizing decision that the parents are forced to make in considering whether to selectively abort their child. It perhaps sounds cruel, but this agonizing is precisely what should not be circumvented. It seems that reproductive technology has advanced to the point that it is not only easier to have a healthy baby, but the ethical issues that it entails are also made easier. In watching the video "Burden of Knowledge", I was impressed by the fact that the prospective parents seemed to take the ethical aspect of their treatment rather lightly. I believe that the in vitro nature of PGD allows for this to happen. Once cells, including sperm and egg cells, are removed from one’s body, there is a feeling that they are no longer part of you. The process of PGD becomes clinical and impersonal and the ethics behind the procedure are perhaps not weighed as much as they should be. Surely the couples would consider the moral implications more had they to choose to abort their child. Sometimes the easiest and least problematic way out of a situation is not the best way. I do not necessarily agree with selective abortion. However, I do think it a relatively better option ethically because it does not entail the potential dangers of genetic enhancement that PGD does.
In dealing with the subject of PGD, one of the hardest elements to face is the testimony and stories of actual people like the Abshires who have benefited immensely from this technology. Their testimony is highly emotional and very moving. But the debate whether PGD is morally justified is at its essence an ethical one that should be examined dispassionately because its ramifications have the potential to effect all of society. I only wish that some of the documentaries on these couples would also depict the many parent-less children at the local orphanage or the mal-nourished and indeed starving children in less fortunate regions of the world. Juxtaposed with these images, their stories seem a little less heart-wrenching and indeed a bit of selfishness comes through. Not only is adoption an ethically unproblematic solution to the couples’s dilemma, it is also one of the best and most generous things one can do as a human being. This obsession and willingness to go to such lengths to ensure a healthy baby that is biologically one’s own perhaps says something about the state of our society. This ultra modern commodity culture has fostered in us an ethos of self-gratification, and a feeling that we deserve to possesses everything, and for the right price, we are able to have it. We need to ask ourselves if this is really medicine or a commodity.
In considering the ethics of pre-implantation genetic diagnosis, I have personally gone back and forth on the issue. In the end however, I feel that the role of medicine is to strive to improve the health and quality of life. It is not to create life or manipulate its inception. The emerging science of genetics promises to provide medicine with incredibly powerful tools to fight disease. Fields such as stem cell research and gene therapy will perhaps someday afford cures to many diseases with which we currently struggle. To use genetic technology to this end not only is permissible, but it would be morally questionable not to. PGD differs from these other methods in that it doesn’t seek to improve an already existing life, but rather to set the terms upon which a life shall be created. There is a line that is crossed here. It may perhaps be an ineffable line but it is one that is nonetheless present. At times we lose sight of the fact that knowledge and wisdom are very different things. To presume that we have the wisdom to dictate the terms on which life should exist is not only arrogant, it is wrong. We can ensure that our children be born completely healthy and perhaps physically perfect, but we shouldn’t.
Works Cited
1. Vines, Gail, "Every Child A Perfect Child," New Scientist, (28 October, 1995), 14-15.
2. Fackelmann, Kathy, "Test-Tube Daignosis," Science News, 146 (October 29, 1994), 286-287.
3. Tasca, Richard, and McClure, Michael, "The Emerging Technology and Application of Preimplantation Genetic Diagnosis," The Journal of Law, Medicine & Ethics, (Spring 1998).
4. Kaufmann, Robert et al, "Preimplantation Genetic Diagnosis," The Journal of Reproductive Medicine, 37 (May 1992), 428-434.
5.Botkin, Jeffrey, "Ethical Issues and Practical Problems in Preimplantation Genetic Diagnosis," The Journal of Law, Medicine & Ethics, (Spring 1998).
6. Gibbs, Wayt, and Beardsley, Tim, "Fertile Ground," Scientific American, (February 1994), 26-28.
7. Rennie, John, "Grading the Gene Tests," Scientific American, (June 1994), 89-97.
8. Winston, Robert, and Handyside, Alan, "New Challenges in Human in Vitro Fertilization," Science, 260 (14 May, 1993), 932-936.