Researchers have explained that the haemolytic disease of the fetus is more accurately detected by ultra sound techniques.
Doctors have claimed in their new study that Rh diseases of the fetus are more accurately detected on using Doppler ultrasound by measuring the velocity of the blood flow in the middle cerebral artery, which is the main artery that supplies blood to the brain. The investigators were of the feeling that as ultrasound is an non-invasive and a safe technique it could probably replace amniocentesis.
It was explained that Haemolytic disease of the fetus usually occurs as the antibodies present in the mother attack a protein called rhesus (Rh) D that may be found in the red blood cells of the fetus. The mother usually develops these antibodies during the first pregnancy and then the problem occurs during the successive pregnancies. RhoGAM, which is the counter-antibody therapy is given to the mother and is generally successful in preventing the problem, thought not always.
The researchers explained in The New England Journal of Medicine, that in pregnancies that were complicated by the 'Rh alloimmunization', fetuses can develop haemolytic anaemia, thereby causing decreased blood viscosity, which results in increased velocities of blood-flow that can be detected by ultrasound. It was also explained that normally a serial amniocentesis specimens would be required, and a diagnosis of anaemia would be based on a technique known as spectrophotometry, which is done to calculate the bilirubin level that is an indirect indicator of red cell destruction.
Dr. Dick Oepkes, from Leiden University Medical Center in the Netherlands, and team of colleagues compared the results of both the methods among 165 fetuses at 10 centres across Europe and North America. Explaining that they found the Doppler ultrasound had a greater sensitivity, specificity, and accuracy for severe anaemia than amniocentesis.
Concluding that Doppler ultrasound "can safely replace invasive screening in the management of Rh-alloimmunized pregnancies," Oepkes and his associates, however also stressed that as the sensitivity of Doppler ultrasound is not 100%, even among experts with vast experience in performing Doppler ultrasound of the fetus and managing Rh-alloimmunized pregnancies. So they stated that the likelihood of occasions when serial amniocentesis will still be required would definitely be present.