Non-invasive diagnosis of fetal anemia due to maternal red-cell alloimmunization

OBJECTIVE: To determine the value of measurement of velocity of the middle cerebral artery (MCA) in the prediction of fetal anemia in alloimmunized pregnancies without ultrasound evidence of hydrops and to see if this could replace the invasive techniques in the diagnosis and management of this condition.

METHODS: In a prospective cohort study, 65 non-hydropic fetuses with red blood cell alloimmunization were evaluated with ultrasound and Doppler imaging. This study was carried out at Feto Maternal Medicine Unit at Women's Hospital, Hamad Medical Corporation, Doha, Qatar from January 2003 to December 2003. Middle cerebral artery-peak systolic velocity (PSV) was measured. We interfered only if there is a sign of fetal anemia as indicated by changes in blood velocity in MCA using the table designed by Giancarlo Mari or the fetus developed signs of hydrops fetalis. Immediately after delivery, the blood was taken from umbilical cord for full blood count, blood group, bilirubin and antibodies level. Results before first fetal blood sampling (FBS) or delivery were analyzed.

RESULTS: Sixty-five patients met the inclusion criteria for the study and were managed. Sixty-three women were alloimmunized with rhesus (Rh)-D antibodies and 2 with anti-C. With the conventional management, all 65 patients undergone amniocentesis to determine bilirubin levels. However, with non-invasive management, 60 women were safely prevented from undergoing invasive testing or invasive procedures. Amniocentesis was performed for only one (1.54%) patient, despite having a normal MCV-PSV which was carried out solely due to the care provider was insisting on this procedure and the result was normal. Planning delivery based on MCA-PSV allowed us to deliver 97% (63/65) of these babies without any signs of severe anemia between 28-38 weeks. Two (3%) of the fetuses were diagnosed as severely anemic with MCA-PSV. In both cases, anemia was confirmed by FBS and intra uterine transfusion was carried out immediately to the test. Only 2 babies were diagnosed anemic after birth and underwent blood transfusion.

CONCLUSION: Doppler evaluation of MCA-PSV is effective in the prediction of fetal anemia in red blood cell alloimmunization. Using this technique will reduce the number of invasive procedures needed with the added risks of these procedures with good fetal outcome.