Amniotic fluid bilirubin as a prognostic indicator in rhesus isoimmunization

The bilirubin concentration in 654 amniotic fluids obtained by amniocentesis of 227 consecutive rhesus isoimmunized pregnancies is determined by the chloroform extraction method. The material is divided in 3 classes reflecting the severity of erythroblastosis. It is found, by means of graphical analysis that corresponding fractiles of the amniotic fluid concentrations of bilirubin in different gestational weeks imply an almost uniform prognosis. In terms of logarithm the various bilirubin fractiles seem to move parallel to and linear with gestational time. A prediction diagram is constructed, making it possible to estimate fetal prognosis from the concentration of amniotic fluid bilirubin.