July 12, 2006

Ultrasound detects anemia in the fetus

NEW YORK (Reuters Health) - Hemolytic disease of the fetus
can be detected accurately by using Doppler ultrasound to
measure velocity of blood flow in the middle cerebral artery,
the main artery supplying blood to the brain, doctors have

Because ultrasound is noninvasive and safe, investigators
believe this test can replace amniocentesis.

Hemolytic disease of the fetus occurs when the mother
carries antibodies that attack a protein called rhesus (Rh) D
that may be found on the fetus' red blood cells. Usually, the
mother develops these antibodies during one pregnancy and then
the problem occurs during a subsequent pregnancy. A
counter-antibody therapy called RhoGAM is given to the mother
and is usually, but not always, successful in preventing the

In pregnancies complicated by so-called "Rh
alloimmunization," fetuses can develop hemolytic anemia,
causing decreased blood viscosity, which results in high
blood-flow velocities that can be detected by ultrasound, the
researchers explain in The New England Journal of Medicine.

Traditionally, serial amniocentesis specimens were
required, and a diagnosis of anemia was based on a technique
called spectrophotometry to quantify bilirubin level, an
indirect indicator of red cell destruction.

Dr. Dick Oepkes, from Leiden University Medical Center in
the Netherlands, and colleagues compared the results of the two
methods in 165 fetuses at 10 centers in Europe and North

They found that Doppler ultrasound had greater sensitivity,
specificity and accuracy for severe anemia than amniocentesis.

Oepkes and his associates conclude that Doppler ultrasound
"can safely replace invasive screening in the management of
Rh-alloimmunized pregnancies."

However, they also emphasize that the sensitivity of
Doppler ultrasound is not 100 percent, even among experts with
extensive experience in performing Doppler ultrasound of the
fetus and managing Rh-alloimmunized pregnancies, so there are
likely to be occasions when serial amniocentesis will still be

SOURCE: The New England Journal of Medicine, July 13, 2006.