Theodor Stefos

Accurate prediction of fetal hemoglobin by Doppler ultrasonography.

OBJECTIVE To assess the feasibility of using the middle cerebral artery peak systolic velocity (MCA‐PSV) to predict the actual value of fetal hemoglobin in fetuses undergoing a first cordocentesis for detection of anemia caused by maternal red cell alloimmunization. METHODS Doppler velocimetry of the MCA‐PSV was performed in 18 fetuses before an initial cordocentesis. Hemoglobin and MCA‐PSV values were expressed as multiples of the median to adjust for the changes that both parameters demonstrate with gestational age. In each fetus we determined: 1) the expected (using a cubic mathematical function describing the correlation between fetal hemoglobin and MCA‐PSV) and the observed (determined at the time of the cordocentesis) hemoglobin value; and 2) the percentage differences between the expected and the observed hemoglobin values. RESULTS Gestational age at the time of the Doppler study ranged from 19 to 31 weeks. On 15 occasions, the fetuses demonstrated anemia. A quadratic relationship was found between the hemoglobin multiples of the median and the percentage differences between the expected and the observed hemoglobin values. As the values of hemoglobin decreased, the percentage difference between expected and observed values significantly decreased (R2 = 0.48, P < .05). The cubic model estimated fetal hemoglobin well in severely anemic fetuses and less well when the fetus was not anemic. CONCLUSION Doppler measurement of the MCA‐PSV appears to be a valuable tool for estimating hemoglobin concentration in fetuses at risk for anemia. The correlation between hemoglobin and MCA‐PSV becomes more accurate as the severity of anemia increases.

Correction of fetal anemia on the middle cerebral artery peak systolic velocity

OBJECTIVE To assess the effect of correction of fetal anemia on the middle cerebral artery peak systolic velocity values. METHODS With Doppler ultrasonography, middle cerebral artery peak systolic velocity was measured in 41 fetuses before and immediately after 54 intrauterine transfusions for severe red blood cell alloimmunization. The fetuses were divided into two groups: 17 fetuses studied at first transfusion (group A), and 24 fetuses enrolled to the study after the first transfusion (group B). Both fetal hemoglobin and middle cerebral artery peak systolic velocity were plotted over the respective reference ranges as a function of gestational age. Both values were expressed as multiples of the median and analyzed with paired t test. RESULTS The values of middle cerebral artery peak systolic velocity decreased in all but one fetus of group B (P < .05). The values of middle cerebral artery peak systolic velocity before transfusion were above the upper limit of the reference range in 60% of the fetuses of group A and in 38% of group B, respectively. After correction of anemia, only one value remained above the upper limit of the reference range. CONCLUSION The correction of fetal anemia with intrauterine blood transfusion decreases significantly and normalizes the value of the fetal middle cerebral artery peak systolic velocity.

Individual growth curve standards in twins: Prediction of third-trimester growth and birth characteristics

The ability of Rossavik growth models, determined from measurements obtained before 24 weeks, to predict third-trimester growth and birth characteristics in normally growing twins has been investigated. Third-trimester values for head circumference, abdominal circumference, and femur diaphysis length were predicted with an accuracy of +/- 6% to 9% (95% to 98% of percent deviations). For thigh circumference and estimated weight, the comparable values were +/- 15% and +/- 16%, respectively. The head circumference at birth was predicted without bias; the random error was approximately +/- 5% (94% of percent differences). Weight, abdominal circumference, and thigh circumference were systematically overestimated (3.1%, 14.9%, and 11.3%, respectively) as a result of differences in prenatal and postnatal measurement procedures. After correction for systematic errors, these parameters could be predicted with random errors of -11.5% to 7.2% (weight), -12.8% to 5.4% (abdominal circumference), and -15.3% to 10.0% (thigh circumference). Growth Potential Realization Index values were found to have means of approximately 100% and ranges from 91% to 118%. These results are similar to those for singletons and indicate that individual assessment of growth in twins can be carried out with the same methods used for singletons.