Esther Sikkel

Non-invasive tests to predict fetal anemia in Kell-alloimmunized pregnancies

To compare test characteristics of ultrasound and Doppler parameters in the prediction of fetal anemia in Kell‐alloimmunized pregnancies.

Fetal cardiac contractility before and after intrauterine transfusion

To evaluate the effect of fetal anemia and intrauterine transfusion on ventricular shortening fraction.

Amniotic fluid Δ OD 450 values accurately predict severe fetal anemia in D-alloimmunization

OBJECTIVE To assess the diagnostic accuracy of amniotic fluid Δ OD 450 values in the second and third trimesters of D‐alloimmunized pregnancies. METHODS We searched our database for singleton D‐alloimmunized pregnancies with nonhydropic fetuses, where amniocentesis was performed within 4 days of first fetal blood sampling. Amniotic fluid Δ OD 450 values were plotted on an extrapolated Lileys chart. Sensitivity and specificity were calculated for two commonly used cutoff levels, Lileys zone 3 and the upper third of Lileys zone 2. Severe fetal anemia was defined as a hemoglobin concentration of more than 5 standard deviations below the normal mean for corresponding gestational age. RESULTS Seventy‐nine pregnancies met our inclusion criteria. Overall accuracy of the extrapolated Lileys curve in predicting severe fetal anemia was 75% (95% confidence interval [CI] 64, 84) for zone 3 and 86% (95% CI 77, 93) when the upper third of zone 2 was included. Sensitivity of Δ OD 450 values in Lileys zone 3 or the upper third of Lileys zone 2 was 95% (95% CI 74, 100) before and 98% (95% CI 89, 100) after 27 weeks. CONCLUSION Lileys extrapolated curve predicts severe fetal anemia with reasonable accuracy and high sensitivity.

Effect of an Increase of the Hematocrit on Middle Cerebral Artery Peak and Umbilical Vein Maximum Velocities in Anemic Fetuses

Objective: To measure the effects of acute large increases of the hematocrit on fetal peak arterial and maximum venous blood flow velocities. Methods: Middle cerebral artery peak flow velocities and umbilical vein maximum flow velocities were measured before, immediately after, and 12–24 h after intrauterine transfusions. All measurements were standardized for gestational age. Results: Complete measurements were obtained at 60 intrauterine transfusions. The mean hematocrit before intrauterine transfusion was 0.19 l/l and after 0.40 l/l. The middle cerebral artery peak flow velocity decreased immediately after transfusion in 59 of the 60 cases. There was a rise in umbilical vein maximum flow velocity immediately after intrauterine transfusion in 37 of the 60 cases. The sensitivity of middle cerebral artery peak flow velocity for severe anemia before intrauterine transfusion was 54% and the specificity 57%. The sensitivity of umbilical vein maximum flow velocity for severe anemia before intrauterine transfusion was 67% and the specificity 57%. Conclusions: An acute large increase of the fetal hematocrit significantly decreases middle cerebral artery peak flow velocity. The effect on umbilical vein maximum velocity is, however, unpredictable.

Bilirubin/albumin ratios in fetal blood and in amniotic fluid in rhesus immunization.

OBJECTIVE: To test the hypothesis that unconjugated bilirubin is equally distributed over the albumin molecules present in fetal blood and amniotic fluid in Rhesus (Rh) immunization. METHODS: Molar concentrations of unconjugated bilirubin and albumin were measured in fetal blood and amniotic fluid samples, obtained before the first intrauterine transfusion in 30 nonhydropic, anti-D–alloimmunized fetuses, with gestational ages ranging from 20 to 35 weeks. RESULTS: Bilirubin concentration in amniotic fluid was best predicted by a combination of bilirubin concentration in fetal blood (P<.001), albumin concentration in fetal blood (P=.008), and albumin concentration in amniotic fluid (P<.001) (adjusted R2=0.91). The bilirubin/albumin ratios in fetal blood were linearly correlated with the bilirubin/albumin ratios in amniotic fluid (R2=0.75, P<.001). However, the bilirubin/albumin ratios in fetal blood were always higher than the bilirubin/albumin ratios in amniotic fluid (regression coefficient 1.4, 95% confidence interval 1.1–1.7). In our population, a bilirubin/albumin ratio in amniotic fluid of 0.10 or greater had a better sensitivity and specificity to predict severe anemia (Z hemoglobin –5 standard deviations or less) than the Queenan 4 or the Liley 2c line. CONCLUSION: The relation between fetal hemolysis and amniotic fluid bilirubin concentration is based on the linear correlation between bilirubin/albumin ratios in fetal blood and in amniotic fluid. The slope in Queenan’s and Liley’s chart follows that of the albumin concentration in amniotic fluid during gestation. LEVEL OF EVIDENCE: III