The value of reference ranges for middle cerebral artery peak systolic velocity in the management of rhesus alloimmunized pregnancies.

OBJECTIVES To establish reference ranges for middle cerebral artery peak systolic velocity (MCA PSV) and to certify their value in the management of Rhesus alloimmunized pregnancies. MATERIAL AND METHODS A reference range of MCA PSV with gestation was constructed by studying 342 pregnancies at 25-40 weeks. A comparison was made between the reference ranges produced in our study and those already published. Fetal MCA PSV was also measured in 30 fetuses from Rhesus alloimmunized pregnancies at 25-39 weeks. Last MCA PSV measurement was made within 7 days before measurement of umbilical cord hemoglobin at delivery. MCA PSV and hemoglobin were expressed as multiples of median (MoM). OUTCOMES In the normal pregnancies a significant increase in MCA PSV with gestation resulted. The reference ranges for MCA PSV in normal pregnancies were similar to those already in use up to 34 weeks. From 35 to 40 weeks, our values were lower. In the Rhesus alloimmunized pregnancies, MCA PSV was increased. We found a good correlation between MoM MCA PSV and MoM hemoglobin. Using a threshold of 1.29 for MoM PSV, the sensitivity and specificity of MCA PSV in predicting any degree of anemia (Hb ≤0.84 MoM) were 88.46% and 98.27%. CONCLUSIONS Our reference ranges for MCA PSV can perform well from 25 until 35 weeks of gestation. Based on this, measurement of the MCA PSV in fetuses at risk for anemia provides a reliable, non-invasive clinical test for the prediction of fetal anemia.