TIME: Almanac 1993/TIME Almanac 1993.iso/time/112789/11278900.023

Text File | 1992-09-23 | 3.7 KB | 77 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.