SINCE THE EXPLOSION of the Hiroshima bomb, scientists have been trying to anticipate the next scientific discovery that could affect the basic realities of life and death all over the world. Having been unprepared for the moral, ethical and even technical ramifications of atomic fission, they wanted to think through the next set of questions before, rather than after, the fact. Beginning with the discovery of the chemical structure of DNA -- the genetic material -- in the 1950s, the accelerating with the recent development of recombinant DNA techniques, which allow individual genes to be separated and manipulated, there has been little doubt that the next area in which scientific advance would shake the foundation of our social values would be reporductive biology.

That reality is already here. Two babies since Louise Brown have been born in vitro fertilization, and last week the first medical clinic for carrying out the in vitro procedure in the United States was approved in Norfolk, Va. But while a few researchers, clinicians and philosophers have thought much about these social and ethical issues, society at large has not begun to grapple with them. If anything, the national debate over abortion has set back the level of clear thinking and understanding of the events of early human development.

During in vitro fertilization, a mature egg is removed from a donor just before it would normally be shed by the ovary, and is then mixed in a laboratory dish with sperm. After fertilization, the egg is observed through the first several cell division, and after several days -- corresponding to the time normally required for the egg to traverse the Fallopian tubes -- is reimplanted in the uterus of a woman. Under current conditions, the egg donor and the recipient of the developing embryo are the same woman, and the sperm must come from her husband -- conditions imposed for social rather than biological reasons.

Opposition to the Norfolk clinic is fierce. Some opponents maintain the in vitro procedure is too manipulative of a biological process. But they ignore the fact that all of medicine is similarly intrusive. Others are concerned because developing embryos that are seen to be grossly abnormal will not be reimplanted. This, however, merely mimics nature: a very high proportion of eggs fertilized normally inside the body are never implanted in the uterus. Finally, there are those who oppose the procedure because it is still experimental -- as all medical treatments are at first -- or because embryos that cannot be reimplanted might be used for research. But why not? Nature routinely discards abnormal embryos, and use of this material could provide immensely valuable and otherwise unattainable understanding of the crucial and still largely unknown events of early human development. The possibility that some misguided doctor might sequester a normal embryo for research purposes, rather than implanting it, is highly remote.

There is a clear medical demand for the new clinic. Somewhere between 300,000 and 600,000 American women are infertile because of blocked Fallopian tubes, and for many of them the inability to bear children is a constant personal tragedy. For these people the procedure would be a godsend. The problem with the clinic has nothing in fact to do with them. Rather, the risks concern the road down which this procedure and the knowledge associated with it are taking society.

A good many steps down that road have already been taken. Research in mammalian genetics and embryology has gone way beyond what is ethically or technically feasible now in humans. For example, normal mice with as many as six parents have been produced in experiments using embryo fusion to reveal information on chromosome structure. The point is not that such things can or will happen soon in humans, but rather that the time for society to begin seriously thinking about these issues has long since some. in vitro fertilization is basically a surgical maneuver to get around blocked Fallopian tubes. In itself it raises few fundamental ethical questions. But other procedures and experiments, involving development of the fetus to full term in the laboratory or alterations of the genes (genetic engineering), do raise them with a great deal of immediacy.

The clinic should be built. But the trade-off for that should be some insistence on the part of medical authorities, religious leaders and others that we begin to get serious and systematic about exploring the ethical issues and setting real limits on the future directions of research and practice in genetic engineering reproductive biology.