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5 FETAL DIAGNOSIS AND THE IMPACT OF MOLECULAR GENETICS David Hoar Early in the last decade antenatal genetic diagnosis was introduced primarily as a means of detecting Down's Syndrome and other chromosomal mutations by cytogenetic analysis. Almost immediately the potential for early diagnosis of biochemical diseases became apparent. Those prenatal testing procedures brought with them a series of new ethical issues. Some groups believed (and still do) that antenatal diagnosis is a "search and destroy" mission directed against the abnormal fetus. The other view is that such testing provides the majority of couples (greater than 90 percent) with reassurance. The recent developments of molecular genetics are rapidly entering into the repertoire of antenatal diagnostic tests. Along with these applications of high technology come the anticipated dilemmas. The problems that are brought to light are often unexpected complex interactions of moral and ethical issues. These issues impinge upon all elements of the interaction among the family, physician, and laboratory. Of importance in this respect is the fact that people have come to the point of insisting, or even demanding, that newly developed research technology be used where they believe it will benefit them. The patients' perception is often based upon the media's popularization of new discoveries. Such new applications must be entertained with caution and should withstand the critical evaluation of peer review and human ethics review. Without these controls there is a real risk of compromise in both scientific and ethical considerations, compromise based upon emotion. My role is to bring forward some of the issues. They raise many questions that deserve answers and a series of specific situations will help define some of these questions. The first deals with the antenatal diagnosis of sickle cell disease . Patients with this disease often get into difficulties in child- 56 Biomedical Ethics and Fetal Therapy hood and have a reduced life expectancy. However, there are individuals with the identical genetic defect that have few or no problems and may have a normal life expectancy. The diagnosis of a sickle cell fetus presents the expecting parents with a question that must be based upon their experience. We have diagnosed five such fetuses recently and the choice of four out of five sets of parents has been to carry the fetus to term. The couple electing termination based their decision upon the wife's experience of growing up with a brother with severe sickle disease. The other cases all had either children with sickle cell at home or one parent with the disease who was obviously not in serious difficulty. The termination of a pregnancy because the fetus carries the same disease as one of the parents or a child in the family presents the most difficult decision. Is the role of the molecular diagnostic laboratory to help these families prepare themselves? If so, how do we justify these expensive testing procedures in light of our escalating health care costs? In some instances it may be possible to predict the basis for asymptomatic sickle cell disease. Thus, detection of the sickle disease gene is primary; however, the modulating mutation holds the key to severity of the disease. In retrospect, our laboratory has been able to use new information to establish the basis for a modulating hereditary persistent fetal hemoglobin mutation in an homozygous sickle disease mother. Her homozygous sickle child (diagnosed prenatally ) did not receive this mutation and hence is expected to develop significant disease. The mother's experience was that sickle disease presented no problems for her and her choice was guided by this. In a second specific case we have the parents' choice based upon the need for a healthy child that could save their slowly dying child. Severe beta thalassemia leads to early death usually by the second decade of life. Treatment involves repeated transfusions and chelation therapy to remove the excess iron received as a consequence of the transfusions. It has been estimated that the lifetime cost of such treatment exceeds $176,000 in 1981dollars even with the reduced lifespan; the cost of prenatal testing per case prevented is about 4 percent of this value. In this situation, the couple in question believed the only hope for their thalassemic infant was to have a normal child to provide tissue for bone marrow transplantation. The fetus must not only be normal (it was a normal carrier) but also be tissue transplant compatible. This is presently only tested post- [3.135.217.228] Project MUSE (2024-04-26 08:15...

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