Prediction of fetal anemia in rhesus disease by measurement of fetal middle cerebral artery peak systolic velocity.
OBJECTIVE
In red blood cell (RBC) isoimmunized pregnancies fetal anemia is associated with a hyperdynamic circulation. The aim of the present study was to examine further the possible value of fetal middle cerebral artery peak systolic velocity (MCA-PSV) in the management of affected pregnancies.


METHODS
A reference range of fetal MCA-PSV with gestation was constructed from the study of 813 normal singleton pregnancies at 20-40 weeks' gestation. Fetal MCA-PSV was also measured in 58 fetuses from RBC isoimmunized pregnancies, with maternal hemolytic antibody concentration of >15 IU/mL at 19-38 weeks' gestation and within 10 days of measurement of fetal hemoglobin concentration in blood obtained either by cordocentesis (n = 43) or at delivery (n = 15). In the RBC isoimmunized pregnancies each of the measured MCA-PSV and hemoglobin concentrations was expressed as a delta value (difference in SDs from the normal mean for gestation). Regression analysis was used to determine the significance of the association between delta MCA-PSV and delta fetal hemoglobin concentration.


RESULTS
In the normal pregnancies there was a significant increase in fetal MCA-PSV with gestation (mean MCA-PSV = 10(0.0223 x GA + 0.963)). In RBC isoimmunized pregnancies the fetal MCA-PSV was increased and there was a significant association between delta MCA-PSV and delta hemoglobin concentration (delta hemoglobin = (delta MCA-PSV + 0.093)/-0.356; R(2) = 0.638, P < 0.0001). An MCA-PSV of mean + 1.5 SDs detected 96% of severely anemic fetuses, with a hemoglobin deficit of at least 6 SDs, for a false-positive rate of 14%.


CONCLUSIONS
Measurement of fetal MCA-PSV is a useful method of assessing fetal anemia. In the clinical management of isoimmunized pregnancies a cut-off in MCA-PSV of mean + 1.5 SDs can identify nearly all severely anemic fetuses with a low false-positive rate.
Scheier
M
M
Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
Hernandez-Andrade
E
E
Carmo
A
A
Dezerega
V
V
Nicolaides
K H
KH
D000740:Anemia / Q000000981:diagnostic imaging*; D001783:Blood Flow Velocity; D003430:Cross-Sectional Studies; D004899:Erythroblastosis, Fetal / Q000000981:diagnostic imaging*; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D005315:Fetal Diseases / Q000000981:diagnostic imaging; D005865:Gestational Age; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011247:Pregnancy; D012044:Regression Analysis; D013599:Systole; D016216:Ultrasonography, Prenatal
D006454:Hemoglobins