July 12, 2006
Ultrasound urged for Rh fetal blood check: study
By Gene Emery
BOSTON (Reuters) - Ultrasound technology is a safer and
more accurate way to diagnose Rh disease than the standard
technique of sampling fluid from a fetus to check for the blood
problem, an international study showed on Wednesday.
is caused by blood incompatibility between mother and fetus,
and once led to thousands of stillbirths and infant deaths each
year in the United States.
The research, the first to compare the two methods, is
important because ultrasound carries little risk while each
sampling of the amniotic fluid, called amniocentesis, poses a
small potential for sparking a miscarriage.
Many medical centers, based on small studies, have begun
favoring ultrasound. The new study, reported in The New England
Journal of Medicine, confirmed that such a strategy was
justified, said a team led by Dick Oepkes of the Leiden
University Medical Center in the Netherlands.
Rh disease, also known as Rh sensitization, develops in
pregnant women who have Rh-negative blood.
If the fetus has Rh-positive blood and the two blood types
mix, the mother's immune system may attack the red blood cells
of a subsequent Rh-positive fetus, causing anemia or other
problems that can lead to death for the fetus as early as the
Treatment can prevent death in 90 percent of the cases.
The new study, at 10 medical centers in Europe and North
America, looked for signs of anemia in 165 high-risk fetuses
using both the standard technique and with ultrasound equipment
that assessed the speed of blood flowing through a large artery
in the brain.
The ultrasound test correctly determined which fetuses had
anemia in 85 percent of the cases. The success rate was 76
percent for amniocentesis.
Ultrasound measurement was significantly more accurate and
sensitive than sampling the amniotic fluid, said the Oepkes
Ultrasound "may largely replace amniocentesis" in the
diagnosis of the condition, said Kenneth Moise Jr. of the
University of North Caroline School of Medicine, in a Journal
Combined with other research, the findings "suggest that
the time has come to put our needles aside when evaluating
affected fetuses," said Moise.
The researchers cautioned that the new results were from
medical centers where the technicians had extensive experience