The last decade's explosion of genetic knowledge, dramatic events such as fertilization of a human egg outside the womb, surrogate mothering and now the possibility that man may be able to rewrite his own genetic code are all contributing to a spiritual fallout on scientists, doctors and patients, as well as members of the clergy.

Although the choices can be excruciatingly painful to the individual, the deeper ramifications of genetic tampering have for the most part been swept aside in the tumult and excitement of the discoveries themselves.

Much public discussion of "medical ethics" has centered on the meaning of death--when to discontinue life support, for example.

But the new genetics call for considerably more examination than can be provided by a sonogram, a CAT scan or amniocentesis. And the decisions about the beginning of life, or a decision to abort a life before it is properly begun, can be accompanied by agonies and guilts that may be alleviated only by truly compassionate and genuinely skilled counseling, apart from the clamor of the controversy.

John C. Fletcher, an Episcopal priest and a practicing bioethicist at the Clinical Center of the National Institutes of Health, believes there is an essential role for the pastoral counselor in the kinds of medical decisions that doctors, patients and families must make today: from the discovery that a person is a carrier of a genetic illness to a decision to seek--or to be--a surrogate mother.

Doctors traditionally have assumed counseling roles with patients and their families, but there is a growing sense, often among the health professionals themselves, that the questions can be moral and medical, spiritual and scientific. Too heavy a responsibility for the doctor, perhaps, and often as agonizing and as spiritually debilitating to him as to the patient. Physicians are trained to regard death as the enemy, to be fought at all costs. Death is regarded by the doctor as failure.

Fletcher's message is "that the doctors don't have to bear these burdens alone. And the temptation to bear them alone is a temptation to omnipotence. If a physician succumbs to that, the physician might make moral judgments and ethical judgments on behalf of others without letting the patient and the family bear their due responsibility."

But this requires that the scientists must know something about religion, and, even more crucial, the clergy must know more about science.

"My work," says Fletcher, "is helping people think more clearly about the moral choices they have to make and helping them be sure they know the reasons on which the choice is based."

He establishes the lines of communication in his eloquent book Coping With Genetic Disorders (Harper & Row, $14.95). The book's subtitle calls it "A Guide for Clergy and Parents," but it is much more--a primer in genetics; a lesson in theology; not the least, some glimpses into the considerable and lucid thought processes of an insightful and caring spirit. It should be required reading for any health professional, clinical or research, or for any patient or potential patient, family and friends, as well as for Fletcher's colleagues to whom it is aimed.

John Fletcher might have been a saint a thousand years ago. Or burned at the stake. He is, as the surfers say, shooting the curl of a new wave--that is, a new kind of thinking about good and evil, about God and human suffering, about scientific breakthroughs and the meaning of life. It is a time when theologists and philosophers and metaphysicians are wrestling with apparent contradictions between what science knows and what faith demands.

Fletcher, 51, considered medicine, but "decided on the ministry instead," although he never lost his interest in the healing sciences. He is the brother of actress Louise Fletcher, who "signed" her thank you's when she won the Academy Award for her role in "One Flew Over the Cuckoo's Nest." Their parents, who now live in Falls Church, are deaf. Fletcher and his wife, a Northern Virginia Realtor, have three children of their own, and live in Alexandria.

John Fletcher would like to see medical advances obviate the need for therapeutic abortions and believes that eventually they will, but meanwhile he believes that "our society should support a woman who could go either way with that decision--to accept a child with a serious handicap and also support a woman who made the choice of abortion.

In his book he writes, "There is a moral problem at the heart of the abortion decision. On the one hand, there is the interest in the life of the fetus. On the other hand, there is the interest of the mother and the parents in protecting themselves from what they interpret to be 'harm.' "

Analogously, he sees "two profound movements in our society: One is the need for women to become citizens and participants in the society in every sense of the word, including the more careful planning of pregnancies, and waiting until later.

"But on the other side, we are reaching a point where the birth of every child is becoming more and more important. If we think 100 years ahead, we could be in a serious bind with long-term zero population growth. These two social needs and pressures can come into conflict--that's the way I choose to listen to the debate about abortion--two valid interests in conflict. And we'll be involved in that conflict for a long time."

Curiously, says Fletcher, in a report he co-authored in this week's New England Journal of Medicine, use of one modern scientific technique--ultrasound--may have the effect of reducing abortions. Scientists have found that the ultrasound image of the fetus stimulates early parent-infant bonding, for the father as well as the mother, "a shock of recognition" of the blurry image as their baby.

Fletcher has also been concerned recently about surrogate motherhood and the ethics involved in this growing phenomenon.

"My position," he says, "goes like this:

"I have no objection ethically to a woman making a gift of herself on behalf of another woman who cannot carry a baby. However, I feel strongly that the commercial aspect of surrogate motherhood as it is developing in the United States is already profoundly dehumanizing. It is selling one's body to bear a baby.

"We consider it unethical to sell one's kidney or one's heart to a person who needs an organ transplant and, under normal circumstances, even consider it unethical to sell one's blood. We've adapted technology under the older concept of gifts. We use the obligation of gift, rather than an economic transaction--both to prevent poor and needy people from mutilating themselves and to prevent their exploitation.

"I think we have to take action to de-commercialize surrogacy and prevent not only exploitation, but particularly the abandonment of unwanted children."

Bioethics is a relatively new field, an amalgam of science and metaphysics and religion--or spirituality, perhaps, because religion per se may not be involved. To its practitioners it can be a vehicle for reconciling God and nature, for maintaining faith in the face of a mutated gene, or a doomed infant, for understanding hard scientific facts in terms of a cosmic ethic.

Health professionals, Fletcher believes, must learn to call upon the clergy or other spiritual advisers for help. And in turn, the clergy must be ready to meet the kind of challenge that can come, for example, from a mother bearing a fetus with Tay-Sachs disease who demands, "How can God let such terrible things happen to little children."

(Some of these challenges will be addressed this spring at a special NIH-sponsored convocation of practicing bioethicists. Not all participants will be clergy, but all must be practicing bioethical counseling under the aegis of a hospital or other institution.)

Fletcher poses a lot of hard questions, in part through actual cases in which he was sought out, and in part through subsequent reflections on his own participation, on the actions he took at the time and on ways he might have spoken or acted differently.

Among those he has counseled: a young Jewish man who, although he knows he carries a recessive gene for Tay-Sachs disease--an always fatal illness of infancy that appears most often among Jews of eastern European extraction--has refused to share the knowledge with his fiance. Another case involved a decision on whether or not to tell two young girls that their father, estranged from their mother, lost his own father to Huntington's disease, a late-onset dominant genetic disease for which the girls--and their own children, should they have any--may well be at risk.

"Genetic disorders," says Fletcher, "also raise profound religious problems," and so his book also is directed at parents, "especially those who have had a child with a genetic disorder and who feel punished. If they are religious, they feel punished by God; if not, by some cosmic force."

Fletcher's goal is to present a religious perspective, "a view of evolution where God doesn't determine everything, but where God is not indifferent to evolution."

"What could be more perfect," he writes, "in the sense of inspiring awe and respect, than a God who can hold the universe together in one society without undermining the freedom of each part? Such a God is worthy of worship, from my point of view; and, furthermore, God is worthy of the worship of free creatures."