Prediction of fetal anemia by different thresholds of MCA-PSV and Delta-OD in first and second intrauterine transfusions.

Background: Our aim was to compare different thresholds of middle cerebral artery peak systolic velocity (MCA-PSV) and amniotic fluid delta optical density (Delta-OD) with fetal hemoglobin (Hb) during first and second intrauterine transfusions (IUT).

Methods: We determined serial MCA-PSV and Delta-OD in 27 red blood cell alloimmunized fetuses who needed IUT. Before the second IUT, MCA-PSV was measured. The sensitivity and specificity of MCA-PSV and Delta-OD were calculated and compared with fetal hemoglobin  levels.

Results: From 27 fetuses, first time IUT MCA-PSV with a normal median value (MOM) cutoff of > 1.29 detected 60% of the moderate and 100% of the severe anemia cases. MCA-PSV of MOM > 1.5 detected none of the moderate and 93% of severe anemia cases. Delta-OD detected 50% of moderate anemic and 80% of severe anemic cases. At the second IUT, 91% of severe anemia cases were confirmed by MCA-PSV with MOM > 1.5 whereas MCA-PSV with MOM > 1.29 confirmed all cases. One case of moderate anemia was de-tected by MCA-PSV of MOM > 1.29 and none were detected by MCA-PSV with MOM > 1.5.

Conclusions: Different thresholds of MCA-PSV have higher sensitivity and specificity for detecting moderate and severe fetal anemia compared with Delta-OD. It also has a high sensitivity at the second IUT.