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Blood Test for Down's Syndrome in First Trimester

From: C-upi@clari.net (UPI)
Subject: Two tests find Down's syndrome earlier
Organization: Copyright 1998 by United Press International (via ClariNet)
Date: Wed Apr 01 15:05:44 PST 1998

                          UPI Science News
        BOSTON, April 1 (UPI) -- Scientists say a blood test can give pregnant
women an early warning that they are carrying a baby with Down's
syndrome.
        The test, which measures abnormal levels of pregnancy-related
hormones, can give signs of Down's syndrome in the first 14 weeks of
pregnancy, earlier than nearly all other screening methods for the
genetic disorder.
        A second study reported independently today, showed that an
ultrasound procedure developed in England can identify Down's syndrome
and other fetal chromosomal abnormalities even earlier, in the first 10
to 14 weeks of pregnancy. Doctors at the University of California, San
Francisco, say the ultrasound procedure measures the fluid accumulation
in the neck of the fetus that causes the swelling that's characteristic
of a chromosomal defect.
        In the first study, which involved 4,412 women, the scientists from
the Foundation for Blood Research in Scarborough, Maine, found that
first trimester testing detected more than 60 percent of 48 Down's
syndrome babies, which were confirmed through amniocentesis or chorionic
villus sampling, the standard diagnostic tests.
        FBR researcher Glenn E. Palomaki says the study shows ``for the first
time in a population from the United States, that we can move Down
syndrome screening from the second trimester to the first trimester.''
        The scientists measured abnormal levels of two proteins -- pregnancy-
associated protein A, and either a hormone called human chorionic
gonadotropin (hCG) or a part of the hormone called hCG-free beta
subunit.
        Other proteins that are accurate in screening later in pregnancy were
not useful at the early stage, says Palomaki.
        The study is published in Thursday's issue of the New England Journal
of Medicine.
        Dr. Felix de la Cruz of the National Institute of Child Health and
Human Development says the study should encourage more use of earlier
screening.
        Dr. de la Cruz, chief of the mental retardation and developmental
disabilities branch of the NICHHD, says there are many advantages to
catching the condition early, including fewer medical complications if
the woman decides to have an abortion.
        But he also says that in the first 14 weeks, there is ``still no
fetal movement, so there is less chance of bonding between mom and baby.
''
        About 2.5 million women have blood tests for Down's syndrome, but
most of the screening takes place during the second trimester, the
researchers say. If the first screen shows an abnormal protein level,
the woman goes on to chromosomal analysis, using accurate but costly
tests that come with a risk of miscarriage.
        Dr. de la Cruz says Down's syndrome is ``the most common genetic
condition causing mental retardation.'' It affects about one in every 1,
000 babies born.
        The second study, involves a novel technique called fetal nuchal
translucency screening. Dr. James Goldberg, director of the reproductive
genetics unit in the UCSF department of obstetrics, gynecology and
reproductive sciences, says it detects 80 percent of Down's syndrome
cases.``
        The screening method, developed at the Harris Bright Research Center
for Fetal Medicine at King's College in London, could also be used to
detect other birth defects, such as heart abnormalities. King's College
researchers say the method has been used to screen more than 100,000
pregnancies in Europe.
 (Written by Mara Bovsun in New York, with additional reporting by
Lidia Wasowicz in San Francisco)