[THE FETAL MIDDLE CEREBRAL ARTERY PEAK SYSTOLIC VELOCITY AS A PEDICTOR OF FETAL ANEMIA IN RH-ALLOIMMUNIZED PREGNANCY]

Rh-isoimmunization is a pathological condition in which the fetal red blood cells of a Rh (+) fetus are destroyed by the isoantibodies of a Rh (-) woman sensitized in a previous event. Despite of the wide spread implementation of anti D-gammaglobolin prophylaxis this is still the most common cause for fetal anemia. Recently, sonographic measurement of the fetal middle cerebral artery peak systolic velocity (MCA-PSV) has been shown to be an accurate non-invasive test to predict low fetal hemoglobin levels. We present a case report of Rh-alloimmunized pregnancy with moderate fetal anemia, followed-up by weekly MCA-PSV measurements.

A 37-year-old Rh (-) negative gravida 3, para 1, without anti-D gammaglobolin prophylaxis in her previous pregnancies, presented at 27+0 weeks of gestation (w.g.) for a routine third trimester scan. Subsequent ultrasound measurements of MCA-PSV confirmed a progressive increase of the peak systolic velocities from 40 to 80 cm/sec, as well as a gradual rise in the anti-D titers. The evidence of developing fetal anemia necessitated elective Caesarean section performed at 35 wg. The neonate was admitted in the intensive care unit and required resuscitation, one exchange blood transfusion and several courses of phototherapy. The patient was discharged two weeks post partum.

There is a strong correlation between the high peak systolic velocities in the middle cerebral artery (MCA-PSV) and the low levels of fetal hemoglobin. The high sensitivity and positive predictive value concerning the development of fetal anemia, as well as its good repeatability, makes this non-invasive test a valuable asset in the management of all pregnancies complicated by severe Rh-alloimmunization.