Medicine: An Early-Warning System

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For many would-be parents, the recent revolution in prenatal genetic testing has created agonizing dilemmas. If the tests reveal genetic abnormalities in the fetus, the mother and father must either have a handicapped child or resort to abortion. At best the choice is painful. For some, it is the worst kind of moral quandary.

Now a team of medical researchers has devised a technique that may eventually help parents sidestep this predicament. Scientists at the Illinois Masonic Medical Center and Northwestern University, led by geneticist Yury Verlinsky, say they can test for genetic defects in the human egg even before it has been fertilized. The technique could enable thousands of mothers with a family history of genetic disorders to avoid giving birth to an afflicted child without having to undergo abortion. Dr. C. Thomas Caskey, president of the American Society of Human Genetics, calls the new method "promising" but stresses that more testing is needed.

The procedure, reported last week at a meeting of the American Society of Human Genetics in Baltimore, is based on analysis of the "first polar body," a small packet of chromosomes sloughed off from the human egg during cell division. First the researchers remove several eggs from a woman's ovaries. Next the first polar body is detached, and a new genetic test called ! polymerase chain reaction is employed to analyze the chromosomes, which are complementary to those left in the egg's nucleus. Eggs that are not defective can then be selected and used in an increasingly common procedure known as in vitro fertilization. This involves placing the eggs in a soup of sperm and implanting resulting embryos in the mother's womb. The main difficulty is that only one in ten tries results in a birth. Yet the success rate may improve, and prefertilization diagnosis could someday be used to intercept defective genes that cause such diseases as Tay-Sachs, cystic fibrosis and thalassemia.

If prefertilization testing is perfected, it could be a blessing for those ardently opposed to abortion. James Bopp Jr., general counsel for the National Right to Life Committee, says he can see nothing wrong with the test, since it does not involve "the taking of an innocent human life." Still, others have raised moral objections to the whole notion of "test-tube babies." The Roman Catholic Church and some conservative Protestant groups oppose IVF as a threat to the sanctity of human life.

Researchers caution that the test remains experimental and will not be widely available for several years. It has been tried on just five eggs from one woman, and none of the embryos developed. Verlinsky attributes this to IVF's failure rate. But his team must repeat the test on many women before convincing doctors that it is accurate and does not damage the ovum.

Even if the method proves effective, the costs are considerable -- up to $6,000 for the analysis and IVF. Moreover, IVF is a taxing procedure that usually requires repeated cycles of medication to enhance ovulation and delicate manipulations to remove eggs and implant embryos.