TIME: Almanac 1990/1990 Time Magazine Compact Almanac, The (1991)(Time).iso/time/112789/11278900.023

Text File | 1990-09-19 | 4KB | 66 lines

MEDICINE, Page 56

An Early-Warning System

Researchers can now identify genetic defects before conception

By Andrew Purvis


    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.

    Still, the technique may be worth the trouble for those who
oppose abortion but not IVF. The procedure may also appeal to
mothers traumatized by past abortions. With current genetic tests,
a pregnant woman waits nine weeks after conception before genetic
analysis. With prefertilization testing, however, the parents could
theoretically know from the start that their child has healthy
genes.