Are fetal bilirubin levels associated with the need for neonatal exchange transfusions in hemolytic disease of the fetus and newborn?

Background: Fetal bilirubin is routinely measured at our center when taking a pretransfusion blood sample at intrauterine transfusions in hemolytic disease of the fetus and newborn. However, the clinical value of fetal bilirubin assessment is not well known, and the information is rarely used. We speculated that there could be a role for this measurement in predicting the need for neonatal exchange transfusion.

Objective: This study aimed to evaluate the predictive value of fetal bilirubin for exchange transfusions in severe hemolytic disease of the fetus and newborn.

Study Design: A total of 186 infants with Rh alloantibody-mediated hemolytic disease of the fetus and newborn treated with one or more intrauterine transfusions at the Leiden University Medical Center between January 2006 and June 2020 were included in this observational study. Antenatal and postnatal factors were compared between infants with and without exchange transfusion treatments. The primary outcome was the fetal bilirubin levels before the last intrauterine transfusion in relation to the need for exchange transfusion.

Results: In a multivariate logistic regression analysis, the fetal bilirubin level before the last intrauterine transfusions (odds ratio, 1.32; 95% confidence interval, 1.09-1.61 per 1 mg/dL) and the total number of intrauterine transfusions (odds ratio, 0.63; 95% confidence interval, 0.44-0.91 per intrauterine transfusion) were independently associated with the need for exchange transfusion. The area under the curve was determined at 0.71. A Youden index was calculated at 0.43. The corresponding fetal bilirubin level was 5 mg/dL and had a sensitivity of 79% and a specificity of 64%.

Conclusion: A high fetal bilirubin level before the last intrauterine transfusion was associated with a high likelihood of neonatal exchange transfusion.