Efforts to improve the means to diagnose and treat human genetic diseases have a long history in biomedical research and medicine. Now, preimplantation genetic diagnosis (PGD) provides a new way to prevent the transmission of certain types of human genetic diseases to the next generation. It is an alternative to elective termination of pregnancies.

PGD is used to test for genetic diseases that are due to defective single genes or abnormal chromosomes within days of fertilization and prior to the establishment of pregnancy. The procedure essentially begins with the biopsy of one or more cells of a cleavage stage or blastocyst stage preimplantation human embryo that has been produced by in vitro fertilization (IVF). In certain cases, PGD can be done on polar bodies—discarded by-products of egg formation containing excess chromosomes—of unfertilized eggs. Then, the cell(s), or a polar body, is placed into a tube for single gene analysis (DNA analysis by polymerase chain reaction (PCR)), or for chromosome analysis by spreading the nucleus of the cell on a microscope slide (fluorescence in situ hybridization (FISH)).

Preimplantation genetic diagnosis (PGD) is a new method of prenatal diagnosis that is developing from a union of in vitro fertilization (IVF) technology and molecular biology. Briefly stated, PGD involves the creation of several embryos in vitro from the eggs and sperm of an interested couple. The embryos are permitted to develop to a 6-to-10-cell stage, at which point one of the embryonic cells is removed from each embryo and the cellular DNA is analyzed for chromosomal abnormalities or genetic mutations. An embryo or several embryos found to be free of genetic abnormalities are subsequently transferred to the woman's uterus for gestation. Embryos found to carry a genetic abnormality are discarded or frozen. Extra normal embryos may be frozen for future transfer or donation to another couple.

The general perception of how innovative assisted reproductive technologies (ART) are introduced is through a carefully controlled series of experiments in an animal model, such as the mouse. Only after the technique has been proven can one consider confirmatory studies on mammals closely related to humans, such as rhesus monkeys or other nonhuman primates. With this background of a peer-reviewed body of well-established published data, there is sufficient foundation and rationale to propose a clinical investigation to a responsible human subjects institutional review board (IRB). IRBs weigh the benefits and risks of the new methods to human subjects, and then consider the appropriate informed consent procedures for the particular case. Only after a large number of clinical studies are performed at multiple sites and are peer reviewed can the efficacy and safety of the innovative approach be clearly evaluated. At that time, the potential therapy can be responsibly offered to suitable beneficiaries.

In March 1996, the General Accounting Office (GAO) issued the report Scientific Research: Continued Vigilance Critical to Protecting Human Subjects. It stated that “an inherent conflict of interest exists when physician-researchers include their patients in research protocols. If the physicians do not clearly distinguish between research and treatment in their attempt to inform subjects, the possible benefits of a study can be overemphasized and the risks minimized.” The report also acknowledged that “the line between research and treatment is not always clear to clinicians. Controversy exists regarding whether certain medical procedures should be categorized as research.”

This problem currently plagues gene transfer research. A few months prior to the GAO report, an ad hoc committee appointed by National Institutes of Health (NIH) Director Harold Varmus expressed similar concerns in its assessment of NIH investment in research on gene therapy.

One of the most important questions in the debate over the morality of euthanasia and assisted suicide is whether an important distinction between killing patients and allowing them to die exists. The U.S. Supreme Court, in rejecting challenges to the constitutionality of laws prohibiting physician-assisted suicide (PAS), explicitly invoked this distinction, but did not explicate or defend it. The Second Circuit of the U.S. Court of Appeals had previously asserted, also without argument, that no meaningful distinction exists between killing and allowing to die. That court had reasoned that if this were so, it would be discriminatory to allow persons on life support to end their lives by removing such treatment, while those who are not connected to life support would be denied similar access to death.